iPhone 6, 64 GB memory, updated to iOS 12.4.5 this morning. I attempted to sync with my Mini afterwards and got an error:
"cannot be synced because there is not enough free space to hold all the selected items (additional 14.10 GB required)".
According to the summary on my desktop, my phone has 12 GB free, so it looks as if it wants to upload about 26 GB total from the desktop to the phone.
I have no idea why it should be so much. I'm on the latest OS update so it shouldn't need to copy an update across. I've checked through my sync settings and can't see anything obvious that would account for the large upload requirement - I'm not in the habit of syncing video to the phone, or anything like that, just occasional music, and I haven't added anywhere near 26 GB of music to the desktop since my last sync about a month ago. I barely have 30 GB total on the Mini and most of that is already on the phone.
Any ideas on how I can figure out what's taking so much space for this sync?