Az összeg a nyilvántartásban szerepel.

A natural breakdown is:

• Az = the
• összeg = amount, sum
• a nyilvántartásban = in the register / in the records / in the database
• szerepel = appears, is listed, is recorded

So the sentence is literally something like:

The amount appears in the register.

In natural English, that often becomes:

• The amount is listed in the records.
• The amount appears in the register.
• The amount is on record.

Hungarian has two forms of the definite article:

• a before a consonant sound
• az before a vowel sound

So:

• összeg starts with a vowel sound, so you say az összeg
• nyilvántartásban starts with a consonant sound, so you say a nyilvántartásban

This is similar to English a/an.

Összeg most commonly means:

• sum
• amount
• sometimes total

In this sentence, the amount is probably the most natural translation, especially in administrative or financial language.

It breaks down into:

• nyilvántartás = register, record, database, official record
• -ban = in

So:

• nyilvántartásban = in the register / in the record system

This is one word because Hungarian usually expresses meanings like in, on, to, from with suffixes attached to the noun.

-ban / -ben is the Hungarian ending meaning in or inside.

Examples:

• házban = in the house
• iskolában = in the school
• nyilvántartásban = in the register

The choice between -ban and -ben depends mostly on vowel harmony.

Here the word takes -ban, so:

• nyilvántartás → nyilvántartásban

Because a nyilvántartásban is its own noun phrase: in the register.

The sentence has two definite noun phrases:

• az összeg = the amount
• a nyilvántartásban = in the register

Hungarian, like English, uses the article separately with each noun phrase when needed.

The basic verb szerepel can have several related meanings, including:

• to appear
• to be listed
• to figure
• to be included
• in other contexts, to perform / appear on stage

In this sentence, it does not mean play a role in the theatrical sense.
Here it means something like:

• is listed
• appears
• is entered

So Az összeg a nyilvántartásban szerepel means the amount is officially recorded or listed there.

Because szerepel is more specific.

• van = is / exists / is located
• szerepel = appears / is listed / is included in a document, list, record, program, etc.

If you use szerepel, you are emphasizing that the amount is entered or present as an item in some record or listing.

So this sentence is not just saying the amount exists in the register physically; it is saying the amount is recorded there.

Szerepel is:

• present tense
• 3rd person singular
• the basic dictionary form of the verb

So it corresponds to:

• he/she/it appears
• is listed

Since the subject is az összeg (the amount), English uses it is listed / it appears.

Because Hungarian normally does not need a separate subject pronoun when the subject is already clear.

Here the subject is explicitly stated:

• Az összeg = the amount

So there is no need for an extra pronoun like it.

Hungarian often leaves pronouns out unless they are needed for emphasis or contrast.

Yes, nyilvántartás is grammatically singular.

But in English, the most natural translation may be either singular or plural depending on context:

• the register
• the records
• the database
• the system

So even though Hungarian uses the singular noun nyilvántartás, English may prefer records in translation.

No, Hungarian word order is flexible, but changing it can change the emphasis.

This sentence:

• Az összeg a nyilvántartásban szerepel

presents az összeg as the topic, and then says something about it.

Other orders are possible, for example:

• Az összeg szerepel a nyilvántartásban
• A nyilvántartásban szerepel az összeg

These versions are all possible, but they do not sound exactly the same in emphasis.

The given version is a natural way to say As for the amount, it is listed in the register.

Not necessarily. Hungarian uses location endings like -ban/-ben not only for physical places, but also for abstract containers such as:

• records
• databases
• documents
• lists
• laws
• texts

So a nyilvántartásban means in the register / in the records, even though this may be an electronic or administrative system rather than a physical place.