Newbie question... I just got my first mac a week ago and have started using Time Machine. When I look at About This Mac>Storage I have 5+GB allocated to Backup Storage on the internal ssd. I had assumed that whenever I attached my external TM drive and do a backup, the disk allocated to Backup Storage would be released but I've noticed it doesnt do this. Assuming now that my original assumption was wrong, when does this allocation get released ? Thanks. Ian.