Hi rain_dog; that's perfectly natural, so as to allow folks to shave some off to get it to their specs. I'd avoid cutting slots deeper, as strings can start to stick and warble. Ideally we're talking having 2 thirds of the string radius inside the groove, a third outside...shave the bottom(not yours, the nut's...er, sorry, I've got myself in deeper water :oops: )..
...anyway, if you over-shave you can always shim underneath.
Though there's a fair bit of info online if you search, best off asking a tech really if in doubt.