If you enter 1s it is correct that you get the whole trash content listed. (Probably every file in the Trash will have an access date older than 1 second.) The conditions are explained in the help text.
But this doesn’t explain the 100G. (Unless you have combined it with the 1s, since these are OR conditions!)
Is the entry field clean? You must only enter the value and the unit symbol like in the screenshot above, optionally a ‘+’ or ‘-’ prefix. In fact, a value without prefix counts as ‘+’ (bigger than or older than),
any other char before the value counts as ‘-’ (smaller/younger). Maybe you have a space character or something in front of the “100G”? [Edit:] Nope, this isn’t true. A space character would be OK, and any other character other than +/- will raise an error. So this can’t be the reason.
If not, are you sure that the listed items are not only a lot of .DS_Store files and empty folders? These are always deleted if you enter any condition (see the last section in the help text).
Just out of curiosity, why the repeat of 12?
Oh, that’s the number of external disks the average Mac user has connected
No, the reason is that I somehow just felt better with a lower number than with 999. If you never want the user prompt to reappear after the first run, just set it to 1.
Let me know if you get it to work.