Have you noticed this more than once, or was it a one time event?
We are aware of one recent update which could have caused a one time increase in notifications that did not meet your actual new activity items, but we don't think it should happen multiple times. If you are seeing it regularly, please let me know.
View attachment 2067535
Can confirm that I'm seeing the same thing. I'm not sure the exact trigger; it's usually normal, but sometimes upon loading the page it displays those phantom notifications, which disappear when I go check on them (as would be expected of ordinary notifications).
Per the numbers in the attachment above, counting back 17 notifications in my "All Activity" tab puts me back between 02/05/2019 and 02/09/2019. Doing the same for "Works Activity" puts me somewhere between 03/31/2019 and 04/02/2019. (The latter dates are the last entry selected if you count back e.g. 17 spaces from the top. The former dates are those of the entry immediately prior.)