Miners Online..

Hey guys, I've been mining for 6 months now and for the first 3-4 months I did so with 2miners as a pool. Lately I've been mining with RavenMiner as a pool and saw a nice difference with coins earned per day. That said, I see that in their website they mention around 5.5k to 6.5k miners online and yet in miningpoolstats website they mention 8.5k to 10.5k miners for RavenMiner.

So what's going on ? Why is this happening ?