A while back I elected to start syncing my Photos on my Mac to iCloud. I quickly ran out of cloud storage (5GB). I have decided I don't want to deal with some of the back & forth confusion between my computer & iCloud.
In Photos > Settings, under the iCloud tab, when I attempt to un-check iCloud Photo Library, a message comes up saying "Your iCloud Photo Library is currently updating." (This makes no sense - the library has long been full). This message has two options, "Turn Off" and "Continue Updating". Checking "Turn Off," brings up a rather disconcerting message: 1,250 low-resolution items will be removed from this Mac. Full-resolution versions will remain in iCloud. So my question is, why would turning off iCloud be cause to remove items from my computer?
Help is much appreciated,
edit: running OSX Yosemite 10.10.5