This morning my iPad synchronized with no problem. I haven't changed anything since then.
This evening sync fails, needing additional 19.30 GB. I had to uncheck music, photos, & videos to get it to sync. Then I checked them again, and got the same graphic showing 2.03 GB free, and it synchronized.
Back to where it was this morning.
"other" is only 1.89 GB. It's taking a while to synchronize my audio, back after deleting it.