no worries Candice, try and get the depth as close as you can for the fret markers as they get harder to sand flat up the high end frets.
Start at the 3rd fret marker and work to the higher frets so with practice the 21st fret marker should almost sit flat with the fingerboard.
Also important to get the right size brad point drill. Do you know the diameter of the markers ? Ones I have used have been 6mm or 6.35mm (1/4 inch)