not enough memory to update
I have an iphone 5s 16Gb and i need to update the ios to 10.2.1 but i get a msg saying i don't have enough memory. i need 610mb. in the summary it says i have 2.5 Gb of space. on a related note, when trying to free up space i went through my music and podcasts and unchecked the ones to remove and watched the slider work it's way down to show how much memory i have freed up usually about 2-3 Gb. so i click apply and it syncs, and just as it finishes syncing the amount of available space just disappears and i end up with about 200mb free. so i try again and remove some more and the bar slides down to show yet more space free, and when it finishes syncing it goes right back up again, maybe a little less than before but still not what it showed when i clicked sync. this has been happening for a few ios versions now. thoughts?
iPhone 5s, iOS 10.2