The parent-paid-interest rate is calculated as an APR (annual percentage rate). When you set an APR for your kids savings, this is the interest rate they will earn based on the amount in their savings for an entire year. We break this down monthly and it automatically adds the interest to your kids savings Greenlight on the last day of each month.
For example, if your child has a balance of $100 this month, and an interest rate of 12%, they will earn $1 that will be added at the end of the month. Their balance for next month will be $101 and will continue to grow at the same interest rate unless you adjust the rate or your kids spend part or all of their savings.