There are multiple APY figures involved in a Maple Liquidity Pool. Each comes from a combination of platform fees, interest fees, and MPL rewards.
APY representing the LP interest is listed on each pool page in the "Your Investment" block on the webapp. This APY is a fixed interest yield based on the borrower terms the pool participates in. It will change with the interest payments and occurrence of defaults.
The MPL rewards APY is found in the "Liquidity Mining" block of a specific pool on the webapp. This is determined by the price of MPL, amount of supply of MPL available and the number of people staking Maple Pool Tokens (MPTs) to earn rewards.
The aggregate APY is determined by the sum of the APY generated by the interest commitments of borrowers and the liquidity mining opportunity.