As folks have said, it depends on a lot of things... type of construction and location within the room are the big concerns.
If you're on a crawlspace (or 2nd floor) on an outside wall that's supported directly to the foundation, then you can likely double the 40psf rating with no issues. Me being the nerdy engineer type, I'd add support under it regardless, as I did with my aquarium.
If the safe has feet, they'll likely sink into normal flooring to some degree. Adding some sort of bearing plate between the feet and the floor can prevent that.
If you put it on a bare concrete slab, you must have some sort of vapor barrier between the concrete and the safe. Else, water will wick up out of the concrete and cause the bottom of the safe to corrode. Sometimes the easiest thing is to just leave the safe on the shipping pallet to create an air gap to the floor.