Answering question for Fret File - for Filing Fret Ends, pencil shape

Product:
Fret File - for Filing Fret Ends, pencil shape

Question:
These fret end files give values of 1, 2 and 3mm. Is that number specified the widest size the file will manage, or the starting width. I have 2.3mm wide frets, should I pick the medium 2mm or wide 3mm file?