How to calculate compound interest?

For example, some borrower 3000 yuan of period moneys not on schedule capture pays, in 3000 yuan of period moneys 1200 yuan are capital, 1800 yuan are accrual, rate of loan annual interest is 5.508% , punish interest interest rate to be.5) of 8.262%(5.508% × １ . Because punish the morrow that ceasing is the day deducting a money that agrees from the contract,rise plan close, assume this borrower delayed two days to still get on money only, so its part of 1200 yuan of capital is pressed everyday 0.02295%(8.262% ／ 360 days) plan receive interest, accrual of two days is 0.5508 yuan; Section of 1800 yuan of interest is pressed 0.02295% plan recover benefit, accrual of the first day is 0.4131 yuan, the following day accrual is 1800.4131(1800 ＋ 0.4131) yuan 0.02295% , it is 0.4132 yuan.