No interest is accrued to the unused amounts. The interest accrued to the used amounts is calculated at the nominal rate
Credit limit: AMD 5,000,000
Amount withdrawn: AMD 1,000,000
Annual interest rate: 21%
The monthly installments shall make AMD 117,500 (where the interest makes 1,000,000*21%/12=17,500 AMD + principal of 10%=1,000,000*10%=100,000 AMD).