John Gill Commentary Numbers 3:43

"And all the first-born males according to the number of names, from a month old and upward, of those that were numbered of them, were twenty and two thousand two hundred and threescore and thirteen." — Numbers 3:43 (ASV)

And all the firstborn males
For such only were ordered to be numbered, and not firstborn females:

by the number of names ;
which were particularly taken:

from a month old and upward ;
for before that time they were not sanctified to the Lord, nor subject to the redemption price:

of those that were numbered of them [were] twenty and two thousand two
hundred and threescore and thirteen ;
22,273 men; so that there were two hundred seventy three more than the Levites, (Numbers 3:39) .