Bonus is calculated daily but bonuses are given out monthly. The daily bonus is a 2.15% APY that is calculated as follows:

Daily Interest = Daily Balance at EOD * (2.15 divided by 365 divided by 100)

For example: if a transaction of $5000 is made on 1st December, considering there are no other deposits or spends for the entire month, the daily bonus accrued at 2.15% APY will be $0.29.

How?

5000 * (2.15 divided by 365 divided by 100) = $0.29. Till 31st Dec, the total bonus becomes 31 days * $0.29 = $8.99.