A jump in that party's hashrate overnight does not change what the network pays out. Difficulty only moves every 2016 blocks, roughly two weeks, so a jump between adjustments raises the party's share of the same reward until the next retarget. Against a network hashing at 967.83 EH/s, 600 PH comes to roughly 0.062%. That is about one block in 1,613 tries, or eleven days at ten-minute blocks. What actually moves overnight is the split inside the pool, fixed per share before the first hash lands.