So my sister sent me a picture of her Russian tortoise and i almost cringed seeing it. She doesn't care for it the right way i noticed this on its shell and wondering what it is so i can at least know what it is before i address it with her. Any help is appreciated!!
That looks like the result of what I call a "slow burn" from having too hot of a basking bulb. This is commonly seen in larger tortoise in warmer climates where a "dog house" type of set up is used with a heat lamp or ceramic heating element. I see it mostly on sulcatas.
Not really anything you can do about it except not make it worse.