Disk Utility Error -69850

I'm trying to erase a 256GB SanDisk flash drive and format it to APFS (encrypted, case sensitive). I'm erasing it using the most secure option (seven pass secure erase), but I keep getting this error: "the chosen size is not valid for the chosen file system: (-69850)." However, when I use the least secure erase option, it works fine. I am running the latest version of macOS Big Sur (11.5) on a late 2015 iMac. I know 256GB is not too large for this format because the 1TB HDD built in to the computer is formatted with the same format I am attempting to use on the flash drive. Is there a solution to this, or am I doing something wrong?