Rebat mengurangkan caj semasa; dengan kata lain, jumlah turun.

Rebat means rebate or discount returned to the customer. It is a common loanword in Malay, especially in business, billing, and shopping contexts.

So in this sentence, rebat is the thing causing the charge or total to become lower.

Because mengurangkan is a verb meaning to reduce something.

• kurang = less, lacking, insufficient
• mengurangkan = to reduce, to make something less

This comes from the root kurang with the verb-forming pattern meN- ... -kan.

A useful way to think about it:

• jumlah berkurang = the total decreases
• rebat mengurangkan jumlah = the rebate reduces the total

So mengurangkan is used when something actively causes a reduction.

Caj means charge, fee, or billing amount.

Semasa here means current or present.

So caj semasa means the current charge or the current fee.

Malay usually puts the noun first and the describing word after it, so:

• caj semasa = current charge
• not semasa caj

Not always. Semasa can have more than one meaning depending on context.

Common meanings include:

• current / present
  Example: caj semasa = current charge
• during / while
  Example: semasa mesyuarat = during the meeting

In your sentence, because it follows caj, it clearly means current.

Dengan kata lain is a fixed expression meaning in other words.

Word by word:

• dengan = with
• kata = word
• lain = other

But as a phrase, it simply means in other words. It introduces a restatement or simpler explanation of what came before.

So the sentence structure is:

• statement 1: Rebat mengurangkan caj semasa
• restatement: dengan kata lain, jumlah turun

Because turun can be used as an intransitive verb meaning to go down or to decrease, especially in simple, direct, or informal phrasing.

So:

• jumlah turun = the total goes down
• jumlah menurun = the total decreases
• jumlah berkurang = the total becomes less / decreases

All are possible, but they differ slightly in tone:

• jumlah turun = short, plain, conversational
• jumlah menurun = a bit more formal or written
• jumlah berkurang = also natural, slightly more descriptive

Yes, it is grammatical and natural, especially in straightforward explanatory language.

Malay often allows a very compact structure:

• harga naik = the price goes up
• harga turun = the price goes down
• jumlah turun = the total goes down

This is a very common pattern: noun + verb.

Because Malay does not normally use articles like a, an, or the.

Whether something is understood as a charge, the charge, a total, or the total depends on context.

So:

• caj semasa can mean the current charge or a current charge
• jumlah turun can mean the total goes down or a total goes down

In this sentence, the context makes the current charge and the total the most natural English translations.

Yes. Jumlah can mean:

• amount
• total
• sum
• quantity

The best translation depends on context.

In a billing or pricing sentence like this, jumlah most naturally means total amount or simply total.

The semicolon links two closely related parts:

• Rebat mengurangkan caj semasa
• dengan kata lain, jumlah turun

The second part is basically a restatement or simplification of the first. The semicolon shows a strong connection between the two ideas.

You could also write it with a full stop or sometimes a comma, but the semicolon gives a neat written style.

Yes. A few more formal or polished versions would be:

• Rebat mengurangkan caj semasa; dengan kata lain, jumlahnya menurun.
• Rebat mengurangkan caj semasa; dengan kata lain, jumlah keseluruhan berkurang.
• Rebat ini mengurangkan caj semasa, iaitu jumlah yang perlu dibayar menjadi lebih rendah.

The original sentence is already understandable and natural, but it is quite compact.

It has two main parts:

1. Rebat mengurangkan caj semasa

   • Rebat = subject
   • mengurangkan = verb
   • caj semasa = object

2. dengan kata lain, jumlah turun

   • dengan kata lain = linking phrase meaning in other words
   • jumlah = subject
   • turun = verb

So the overall structure is:

• [thing causing change] + [reduces] + [what is affected]; in other words, [result]

That makes the sentence easy to follow once you know the key vocabulary.