Cloud Backup - different file size

Windows 11. Norton 360 version 24.8.9372
I have backed up my documents folder to the cloud. When right clicking on my documents folder in windows the file size differs from the file size that is in the cloud. It is always less in the cloud, not just the backup of my documents but of my pictures too. ?
Also i cant create a new backup set, am i right in thinking Norton are aware of this problem ?