The Windows recycle bin is a hidden folder that may not have the same name and path from computer to computer, although it most often seems to be called:
C:\RECYCLED or C:\RECYCLER
The recycle bin shows up as a regular folder in Remote Backup's Explorer view (the standard interface) with a ghosty icon and the name of the folder. You can Exclude it like a regular folder.
I wonder WHY it is being backed up in the first place? The reason is probably because your user has selected the entire drive to be backed up - something that is specifically recommended against.
If you use RBackup's AutoSelect feature to select files to back up, or if you select specific folders to back up (like we suggest) you won't back up the recycle bin unless you select it or one of its parent directories.
RBackup's Backup Exclusions list contains a list of items that will be excluded from backups, and they will also be excluded from the file selection menus. By default, the recycle bin is included in the list.
You can edit the exclusion list in the Web Console, Remote Manage Endpoint.
You can also set defaults for your installers in Customize Endpoint Installers -> Backup Sets.