Garmin Express leaves behind download files (firmware upgrades & map updates) in the directory \ProgramData\Garmin\CoreService\Downloads.
This is just taking up space, which can be a problem on SSD discs.
The installer should in fact delete these old download files, or there should at least be an option to do so.
See also thread:
https://forums.garmin.com/showthread.php?273952-Old-files-in-ProgramData-Garmin-CoreService-Downloads