trying to update iPhone to 14.3 on airmac

Hi,

I am trying to update my iPhone 6s to iOS 14.3 and i don't have enough space on my phone so i hooked it up to my airmac and tried updating through iTunes. When i try to update i get an error message saying i need at least 770MB free on my iPhone to update but my phone it showing 835 mb free. I have offloaded pretty much every app i can on my phone. When i check my phone storage (through my phone) it shows i'm using 15.2 out of 16gb. Also if its helpful I have no music on my phone but i have many photos and i think my iCloud storage is full. I have tried restarting my phone and laptop,at the same time.

Thank you in advance for your help!