Both.
(EDIT: At least I think it's both. The latter for sure, but I get a pretty strong vibe it's both. If I was crazier, I'd click and reroll the game again and again to see if it's possible to have the first click be a mine. At the very least I know it doesn't give you a zero on the first click like a good chunk of Minesweeper games do, one of the maps that generated for me, I had to make like 7 blind first-clicks before I finally clicked a zero.)