Seems to be a popular question. I give mine a pile about the size of the and adjust as needed. If there's left overs, I cut back...if the bowl is clean, I add more.
Tortoise graze so put more than it can eat in one sitting . You can even put food in different spots to make them find it . Keeps them moving and is more natural .
I've been putting bits on his cuttlefish, he seems to like that idea I've been keeping his food bowl topped up he doesn't always eat it all but when he eats he goes on a mission! Just don't want to over feed lol
I've noticed that when you feed more natural food (grasses, weeds,etc.), they seem stop more naturally, but if you give them "junk food"....that seems to go out the window. How very human!