Wiktionary
take a number
vb. 1 Queue; wait to be served by being assigned a number and waiting for that number to be called after all previous numbers have been served in order of assignment 2 (context idiomatic English) recognize that many others are in the same situation; recognize that one's concerns are not of high priority; be prepared to wait.
Usage examples of "take a number".
A battered notice told us to take a number and we would be called.
As it passes--and it would take a number of years to pass--it would give a gravitational push to the system.