Manual says to use drill bits as gauge but numbers?

A #52 bit is .0635" which is 1 thousandth of a inch larger than a 1/16".
A #38 bit is .1015" which is .0079 (almost 8 thousands) smaller than 7/64" .
Are you setting float or choke pull off? Either way, I wouldn't worry about a few thousands of an inch.