IPAD tells me I don’t have enough storage space when I actually do

Why does my iPad keep telling me I don’t have enough device storage space when I actually do?

For over a month now, my iPad keeps having a message pop up occasionally saying that I do not have enough storage space for all my photos and I need to optimize them. I have a 32 gb iPad with 16 gb free space. I have less than 2 gb of photos. The pop up message is referring to my device storage space, but I also have more than enough iCloud storage space as well. I even started over by deleting all photos (and then deleting everything in the “recently deleted” folder as well), but am still having this problem. I have my photos synced between my iPhone and iPad, but never receive messages like this on my phone (my iPhone has the same less than 2 gb of photos as my iPad).