number in
To be a part of and add up to some larger, unspecified amount ("the tens," "the hundreds," "the thousands," etc.). Protesters numbering in the marched to oppose the controversial policy. The flock of birds, numbering in the hundreds at least, was so massive that is seemed to actually blot out the sun.
number in something
to total up to a certain figure. The birds numbered in the thousands. These pesky ants number in the hundreds. Let's move to another picnic table.