Imagine the rewards pool as a bucket or keg with a spout on the bottom. Each day a certain amount of rewards are being put into it by the network. In HF 18 our spout wasn't big enough to empty the rewards faster than the reward bucket was replenished every day so it started to get more full.. In HF 19 we've essentially taken the spout at the bottom an replaced it with a much bigger one.. Allowing us to actually possibly drain the rewards pool as fast or faster than it gets replenished. :)