Idk exactly, but the root itself goes like an inch or so into your toe.

Kinda like you, I've got random spots where the root grows and piles up, but since most of the root is dead, it's only like one or two spots on the whole toe. One of them is bad enough that once a year or so it annoys/hurts enough that I remove the offending nail and end up pulling part of the root out. Looks like a newborn horn off of an animal lol