You don't want the strings full diameter below the top of the slot except for the B and treble E.I thought I had put in a line about "opinions vary" regarding how much string is exposed (or not) above the nut, but apparently I only thought it, but didn't type it. So, there you go... two different opinions.You definitely don't want the top of the nut too high above the strings, but exactly how much string is showing (if any) above the top, is really a matter of personal preference e.g. I file down so the nut is level with the top of all the strings.