I've recently added my iMac Photos library to iCloud, so now my iMac, MacBook and iPhone are all in sync on iCloud.
Only issue is, there seems to be a glitch where my MacBook is remembering it's old library size in it's status bar, however it does know that there are 37,750 total items (which is the correct size). See the screenshot attached. I've checked and it does have all the photos.
iCloud on the web also notes the correct, larger library size.
I have done the "Referenced" and "Unable to be uploaded to iCloud" thing, and this is not the issue, they are all in the cloud.
Is this just a glitch that should sort itself out with time (further software updates perhaps)?