Message saying there is not enough free space on my Mac to sync my iPhone, when there definitely is.

Recently I've been having some problems trying to sync my iPhone with my Mac. I get a message saying "The iPhone cannot be synced because there is not enough free space to hold all of the items on your Mac".

My iPhone is 64GB. The free space on my Mac is over 380GB. Surely I don't need to keep over six times the size of my iPhone free on my computer forever if I want to sync my phone.

I've tried to clear as much space as I can, but I store most of my files on the Cloud. I've done everything I can to try and free up more space, but it's not enough. At this rate, I'll have to start deleting entire programs off my computer to clear enough space.

I briefly resolved the issue yesterday when I updated my phone. After doing so, I was able to sync again no problem. Went to try again today and the problem has returned.

I've tried checking the "Back up your most important data on your iPhone to iCloud" option, as opposed to the "Back up your data on your iPhone to this Mac" option, but it makes no difference.

Anyone encountered this issue and know how to fix it?