Summary
Change all occurrences of number | string types to only allow number
Why?
It's confusing accepting both. I realize this was probably done to pave over whatever craziness the DOM might return, but I think pushing a parseInt into consuming apps is worth the type checking cleanliness.
Especially when it's inconsistent with EuiRangeInputProps which only accepts number for min and max which means to validate that your value falls in between your min and your max you have to jump through a bunch of hoops with types.