The APR of Reward Pools shown on the website is an estimate and average calculated by using the current staking amount and bridgings from the last 7 days (except for the initial days after a new token listing when no 7-day history is available. In this case, the longest available period between 24 hours and 7 days is taken). The actual Rewards depend on the amount staked as well as the size & amount of bridgings that occur in the future. The greater the amount staked and the size & amount of bridgings, the higher the collected protocol incentive or bridging fees, meaning the higher the rewards.
The fees dedicated to Reward Pools will be randomly sent roughly once per day (if a transaction occurs).