Learn Hardcore Indonesian: Di laci atas, saya menyimpan pulpen, pensil, penghapus, dan selembar kertas cadangan. - In the top drawer, I keep a pen, a pencil, an eraser, and a spare sheet of paper.

di laci atas = in the upper/top drawer.
di atas laci = on top of the drawer (on its surface). So the sentence says the items are inside the top drawer, not placed on the drawer.

Is laci atas natural, or should I say laci paling atas / laci teratas / laci yang atas?

All are possible:

laci atas = the upper drawer (very common in everyday speech).
laci paling atas / laci teratas = the very topmost drawer (clear and slightly more precise).
laci yang atas = “the one that’s upper/top” (colloquial, also fine). If there are many drawers and you want to be unambiguous, use laci paling atas or laci teratas.

Why is there a comma after Di laci atas? Is it required?

Yes, when you front a place/time phrase, Indonesian commonly uses a comma: Di laci atas, … This follows standard punctuation practice and improves readability.

Should there be a comma before dan in that list?

In standard Indonesian, you normally do not use a serial comma before dan in a simple list. Many editors would write: pulpen, pensil, penghapus dan selembar kertas cadangan. The extra comma is increasingly seen (influenced by English), but it’s usually omitted.

Why use menyimpan here? How is it different from menaruh or meletakkan?

menyimpan = to store/keep (suggests a regular place or for future use).
menaruh / meletakkan = to put/place (neutral, can be temporary). Your sentence implies these items are kept there as their usual storage place, so menyimpan fits well.

Does the sentence show tense (habitual vs. right now)?

Indonesian doesn’t mark tense morphologically. Without time words, saya menyimpan most naturally reads as a general/habitual fact (“I keep …”). Context could also make it mean a present arrangement.

What does selembar do? Why not say satu kertas?

Indonesian needs a classifier for countable units of paper. lembar is the classifier for thin flat sheets.

selembar kertas = one sheet of paper.
Saying satu kertas is ungrammatical/nonnative; use satu lembar kertas or selembar kertas.

Is selembar different from satu lembar?

Both mean “one sheet.”

selembar is the fused, very natural form.
satu lembar is also correct and can emphasize the number a bit more.

Can I say sebuah kertas?

Generally no. buah is a generic classifier but sounds off with kertas. Use selembar kertas. You might see sebuah kertas in learner speech, but natives avoid it.

What does cadangan add? How is it different from tambahan or kosong?

cadangan = spare/backup/reserve (kept for later just in case).
tambahan = additional/extra (more of something).
kosong = blank/empty (no writing).
So selembar kertas cadangan = a spare sheet (implying “backup”). If you want “a spare blank sheet,” you could say selembar kertas kosong untuk cadangan.

Is pulpen the same as pena or bolpoin/bolpen?

pulpen = general “pen” in everyday speech.
pena = more formal/literary “pen.”
bolpoin/bolpen = specifically “ballpoint pen.”
All are understood; choose based on formality and specificity.

Does penghapus mean a pencil eraser or a board eraser?

It can mean either. Context usually makes it clear. To be explicit:

penghapus pensil / karet penghapus = pencil eraser.
penghapus papan tulis = board eraser.

Do I need to mark plurals like pulpen-pulpen or pensil-pensil?

No. Indonesian usually leaves plurals unmarked. If you need to show plurality, use quantifiers or numbers: beberapa pulpen, dua pensil, banyak penghapus. Reduplication (pulpen-pulpen) is possible but less common in everyday lists like this.

Can I drop saya?

Not in this exact structure. Di laci atas, menyimpan … sounds incomplete. Keep saya, or restructure:

Kusimpan pulpen … di laci atas. (ku- = my/I)
Di laci atas, disimpan pulpen … (passive; sounds impersonal/formal).

Can I move Di laci atas to the end?

Yes: Saya menyimpan … di laci atas. Same meaning. Putting the location first adds emphasis to the place.

How is menyimpan formed from simpan? Why the ny?

It’s the meN- prefix + root. Before an initial s, meN- becomes meny- and the s drops: meN- + simpan → menyimpan. This is a regular assimilation rule.

Why di, not ke? Could I ever use ke here?

di marks location (where something is/kept).
ke marks destination (where something goes).
With menyimpan, you usually state the resulting location with di. If you focus on the movement, use a verb like memasukkan … ke laci atas (“put into the drawer”).

Is pada okay instead of di here?

For concrete physical location, di is the natural choice: di laci atas. pada is more formal/abstract (used with times, recipients, or in legal/official texts). pada laci atas would sound stilted in everyday usage.

If I want to specify exact quantities for pens/pencils, how do I say it?

Use a number + (optional) classifier:

sebuah pulpen / dua buah pulpen (buah = generic classifier; fine for pulpen)
sebatang pensil / dua batang pensil (batang highlights the pencil’s long shape)
You can also say dua pulpen and dua pensil without classifiers in casual speech.

Why is the adjective after the noun (e.g., kertas cadangan)? Could I say cadangan kertas?

Indonesian adjectives and descriptive modifiers normally come after the noun: kertas cadangan. cadangan kertas would mean “paper reserves/stock” (a different structure/meaning) and not “a spare sheet of paper.”