The variable you entered (e.g. #Fa01#) is multiplied with the amount in Installment Amount field.
Whenever using a formula to calculate credit amount, it is not returned but a negative amount in the field for unpaid credit amount.
Of course, the negative sign is not used here. It is just displayed because there is no amount recorded from which paid installments could be deducted.

PANTHEON 5.5 Guide:

• Employee Files - Credits

Related topics:

• Employment