Sy pas die rekening aan en stel dit reg.

Here Sy means she.

A useful thing to know is that lowercase sy can also mean his in other contexts, but not here. In this sentence, Sy is followed by the verb pas, so it has to be the subject pronoun she.

• Sy pas die rekening aan = She adjusts the account/bill
• sy rekening = his account/bill

Because aanpas is a separable verb in Afrikaans.

The full verb is aanpas = to adjust / adapt / modify. In a main clause, the verb splits:

• pas goes into the normal finite-verb position
• aan moves to the end

So:

• dictionary form: aanpas
• main clause: Sy pas die rekening aan

This is very common in Afrikaans.

Compare:

• Sy wil die rekening aanpas. = She wants to adjust the account.
• Om die rekening aan te pas... = To adjust the account...

Yes. Regstel is also a separable verb.

Its dictionary form is regstel = to correct / fix / put right.
In a main clause, it splits into:

• stel
  • object + reg

So:

• Sy stel dit reg. = She corrects/fixes it.

Just like:

• aanpas → pas ... aan
• regstel → stel ... reg

Because dit means it, and it refers back to die rekening.

This works just like English:

• She adjusts the account and corrects it.

Instead of repeating die rekening, Afrikaans uses dit to avoid sounding repetitive.

You could repeat the noun, but dit is more natural here.

Because regstel is split in a main clause.

The pattern is:

• stel
  • object + reg

So the object dit goes between the two parts of the verb.

Examples:

• Sy stel dit reg.
• Ek stel die fout reg.
• Hulle stel alles reg.

This is the normal word order for separable verbs in Afrikaans main clauses.

Rekening can mean several related things, depending on context:

• account
• bill
• invoice
• sometimes statement

So the exact English word depends on the situation. In financial or business contexts, rekening is a very common word.

Also:

• die rekening = the account / the bill

They are similar, but not identical.

• aanpas means to adjust, modify, adapt
• regstel means to correct, fix, put right

So the sentence suggests two steps or two aspects:

1. she adjusts the account/bill
2. she fixes/corrects it

Using both verbs gives a fuller sense than either one alone.

Because the subject is the same in both parts of the sentence.

Afrikaans, like English, often leaves out the repeated subject in coordinated clauses:

• Sy pas die rekening aan en stel dit reg.

This is understood as:

• Sy pas die rekening aan en sy stel dit reg.

But repeating sy would usually sound less natural unless you wanted emphasis.

It is in the simple present.

• Sy pas ... aan
• (Sy) stel ... reg

In Afrikaans, the simple present often covers meanings that English expresses with either:

• the simple present: She adjusts it
• or the present progressive: She is adjusting it

So the exact English tense depends on context.

You can use that as a rough memory aid for the structure, but not as natural English.

The separable particles:

• aan in aanpas
• reg in regstel

are part of the verbs, not separate words with their full everyday meanings.

So it is better to learn them as whole verbs:

• aanpas = adjust
• regstel = correct / fix

That will make the sentence much easier to understand naturally.