I've seen it a couple times today while monitoring the block explorer. It will drop for a bit then bump back up to over 200.
I know I'm not on a different chain because the wallet on the blockchain and on my pc are showing the same info and I'm getting deposits from stonerpool on my pc.
Another thing I don't yet understand about this stuff.. lol
the wallet/network have actually no way to monitor what miners are online, all it can do is calculate an average
look in the code for it, and maybe post it on here for all to see, if you don't feel like looking for it let me know and i will post it.