my guess is the safe has a pretty tough paint finish plus heavy/thick steel.... I think the paint on the bottom will be hard to scratch thru...My concern is that moisture may collect causing rust where bottom paint may have been abraded in moving. In most cases people would probably never note any rust even in moving, so I don't know how frequently this happens.
clean and sweep the location, install the safe in dry conditions (dehumidify the garage first). If you really want to you can caulk around the bottom and wall....?