iOS Backup Size plus Next Backup Size? If I have a limit of free 5GB iCloud, and the Backup Info states: 


Backup Size: 4.28GB
Next Backup Size: 1.10GB


Doesn't this mean the next backup will be smaller? Therefore, shouldn't it overwrite/delete the existing backup and thus still be within the 5GB limit?

My backups keep failing because of lack of space.
This means your current backup size on iCloud is 4.28GB.  The next time a backup is done it will add an additional 1.10GB.

4.28 + 1.10 = 5.38GB.  That will exceed the amount of space you have in iCloud.

You can reduce what's being backed-up or buy additional storage space in iCloud.  Check out this answer to a similar question for tips on what you can do.