Less space on drive after deleting files

iMac backup shows 216GB available. Current ssd drive shows only 170GB available in spite of having deleted nearly 60GB since the backup! Folders (vis and invis) on my active drive smaller but the drive shows less available space. Why? I deleted cache and log files along with a huge Warcraft folder but the available space didn't go down and my current drive shows nearly 50GB of less space than my backup which has much larger folder sizes showing. I can only account for about 180GB of data by adding up all my folder sizes. I know APFS does odd stuff but why my backup would show more free space in spite of holding nearly 60 or more GB of files I've just deleted seems very very odd. Thoughts?