221% interest added to closing balance of R29.91

Good day, I received my statement from Consumer friend - Capital Data is the credit provider. On the statement my closing balance is R29.92 on the 23.12.2025. On the 31.12.2025 they process interest of R66.17 which is 221% interest added to R29.92, then you add 5% interest monthly after that which correct but how is the R66.71 over 10 days correct and according to them it is correct. Yet the statement clearly states 5% pm,Can someone from Capital Data and Consumer friend please explain how R66.17 interest over 10 days is correct or possible? How is it correct that you can add 221% interest when the interest cannot be more than the principal amount?