syncing with this computer will replace media...... message

interesting - I did sync it with my last computer, but that was months ago and since, ive been syncing with current laptop. I guess now with all the new iOS updates, you can only use 1 computer for the life of the device. I hope I won't get this message until I get a replacement iPad?!? It also now shows I have double the storage(or these abouts) being taken up on my iPad with my synched photos than the space being taken up on my phone. aprox 10,000 photos being synced and they take aprox 16 gig on the phone and a whopping 30gig on the iPad. Oh boy, now what do I do?

ok, so I did the sync and replace and nothing changed - content wise. I continued to get the same message so I decided to update the os to 13.4.1 as I was 1 or 2 behind. during the update I got an error message, the iPad could not be updated, known error (9).... So I restarted and tried again. This time it went through - however, now I continue to have conflicting HD usage amounts for pictures. Before it showed I was syncing aprox 32 gigs while for the same amount of pics aprox, on my phone im using 16 gigs. NOW my iPad shows 32 gigs of photos while in finder it shows 2.73 for the same amount of pics! What gives? Why the difference? Almost 10k of photos and finder only recognizes 2.73 gigs - impossible. Where is it getting this info from?