Recycle bin fills up my ReadyNAS

It's powered off every night with automatic on/off, and has been rebooted maybe once every 2-3 weeks. The files in the Recycle bin seemed to be #1,#2,#3 up to maybe #100 or so (i have, as I said, deleted them) of I think every file that ever was backed up, like Outlook.pst files (about 30 Mb each), and jpg images (about 2 Mb each). It seemed like several copies of every file ever backed up and took hours to delete. That is a large number of files sized from very small to fairly big (I didn't have any movies or other Gb-sized files in the folders I backed up). The program (NTI Shadow) initially was set to make a backup whenever a file was changed, but later I changed this and made it backup once every evening.