Residual principal: the amount of prepayment usually includes residual principal and prepayment interest. If part of the principal in your previous repayment plan has been repaid, the remaining principal is less, and the amount of prepayment may be lower.
Interest rate change: If the mortgage interest rate is reduced, you may think that the amount of prepayment will be reduced, because the lower interest rate means less interest expenses. However, banks may have their own calculation methods and may increase the amount of prepayment to cover possible risks and costs. The bank may recalculate the prepayment amount according to the new interest rate and repayment plan.
Prepayment fee: Some banks may charge prepayment fee, which will also affect the amount of prepayment.
In order to understand the specific reasons, you'd better contact your bank or lending institution directly and ask them why the amount of prepayment has increased. They can explain the changes in calculation methods and policies and provide you with clear information. In addition, you can also check your loan contract to see if it includes the relevant terms and conditions of prepayment.