number in

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.
See also: number
Farlex Dictionary of Idioms.

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.
See also: number
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • flush the birds out of the bushes
  • a box of birds
  • enough (food) to feed Coxey's Army
  • flock
  • birds of a feather
  • birds of a feather (flock together)
  • BOF
  • increment by
  • over there
  • it/that depends