The shell is looking ok now, it looks bad but the flaking and damage you see is old damage. The way this "heals" is by growing a new layer of shell over the injury. I think most of the white stuff is old dead bone. If the top layer of bone is damage by whatever damaged the shell, then the new shell can grow under it, eventually it looks like what you see, with a thin layer of bone over the new shell.I have a Russian tortoise that has some white stuff on its shell and I’m not sure what it is. Could anyone tell me if it’s shell rot? I’m not sure about the age of my tortoise but it’s not adult sized yet, he gets calcium supplements 2x a week, and lives outside as I’m on Oahu.