She went down over two feet. They have a big one also that will take a 4"swath in one go. Things weighs 14,000 pounds and runs by a 4 cylinder diesel. He made it himself. Needless to say nothing stops that beast.
Probably didn't take long to grind yours. My son has a stump grinder but real small the size of a lawn mower but still pretty aggressive. I would guess that big one would not even bog down.