The APY is calculated from the reward yield (a.k.a. rebase rate) using the following equation:
It raises to the power of 52,560.00 because a rebase happens 144 times daily. Consider there are 365 days in a year, this would give a rebase frequency of 365 * 144 = 52,560.00
APY = (1 + rewardYield)^52,560.00