I believe it has to do with how many you match. I might be mistaken here, but I think during the stretch where you'd get about 19000 for 2, I think if you are lucky enough to get 3 that match, it would be 19500np. So if you had 3 that matched yesterday, and 2 that matched today, it would go down to 19000np. I've NEVER gotten a 4 match. So I have no idea what happens then! XD Oh, and I think the terrible Bonus, which you sometimes get when none match, would bring it to 21000np. Again, I'm relying on a rather unreliable memory here. ;)
Imho, the COOL thing about if you play every day. Since the cycle is 25 days to the big payout of 100k, eventually, a month will come up where you can get the 25th day twice in the same month! Since most months have either 30 or 31 days, not counting February of course. ;)
It's an interesting reason they gave us to check into Neo at least once a day. ;) I check in a bit more often, for dailies, and a couple on-site things mostly. But hey, at least a couple hundred thousand NP a month from Trudy's Surprise per month is a good reason to check in imho. ;) That's more than I generally make from what little gaming I do these days. lol I still battle though. XD