Change in Loan Repayment Installement for current month

I have done live run for the month of June that is 100 for Repayment Installement

After changing amount to 200 for Repayment Installement in the month of July When I do test run It is deducting 200 but it is not deducting previous amount + current amount that is 300 from total loan amount granted.

How would i do that process