On a modification transaction, why is the Current Balance defaulted to the Amount Paid on Loan Account with Payoff and Payment selected?

For non-seller transactions, this reduces duplicate data entry that would otherwise be required for Calculating Cash to Close. Once you change the value in the field it will no longer default from the Current Balance. You will be responsible for entering and maintaining desired values.

An example of when a change may be necessary could include, but is not limited to, circumstances where there is an additional disbursement beyond the current outstanding balance of the loan being modified such as a loan or credit card payoff.