Software :: How Can Change Seven Day Rotating Backup To Copy All Files

I am using Retrospect 6.1.126 and created a 7 day rotating backup -- on the first day's backup all the files I wanted were backed up to my external hard drive, about 80 GB. On day 2 instead of just backing up the modified files as in a normal backup, all the old files were backed up again, another 80 or so GB. On day 3 the same thing. I now have 267 GB on the external hard drive, at that rate it will be filled in another few days.ow can I change the 7 day rotating backup to copy all files on day 1 and on all subsequent days to only copy modified files as in a normal backup?