When a payment is made on the payment screen, the deduction from users balance is conducted, and the transaction is in a pending state.
At this point, the payment amount is not yet recorded as merchants sales.
The transaction is completed when merchant captures the amount separately, and the amount is recorded as merchants sales.
Refer to the URL below to change the amount to be captured from the amount upon payment:
Can the amount be changed before it is fixed for PreAuth & Capture?