Taking the Omega as an example, once I reckoned up that, given the length of the thing and a rough estimate of how heavily built it was, it should have ballpark mass of eighty million tons.
How many crew does it take to look after X amount of ship? A couple of estimates- a WW2 warship, varies drastically, but in general somewhere from 30-50 tons of ship per man, bigger ratio in the bigger ships, some nations crewed more heavily than others. (For instance, Hood and Bismarck were within a couple of thousand tons of each other deep load, forty- eight versus fifty thousand tons, and the German ship had nine hundred and eighty more crew.)
Modern missile warships, again national variations- an Arleigh Burke is more than twice the size of a Type 42 and roughly four times the crew- depending on how undermnned the 42 is- but roughly, 10-15 tons per man.
Spaceships have to be much more heavily automated than that, or we'd be talking about drafting the population of London to crew an Omega. But they're not vastly so, we don't see anything like hypersophistication on screen, so it's not that high. One man for a thousand tons of ship- averaged out over all capacities- that seems feasible. Total blue- sky of course, but it's a round number that'll do as a basis. That still means you need eighty thousand crew for an Omega, which puts one crew factor at thirteen hundred bodies.
That really doesn't feel right, but B5's ships are so huge that we're looking at huge numbers to match for the personnel. You just can't have something that big without the consequences of it's being that big. Bump it up by another factor of ten, call it six to eight thousand- there's enough ship to go round, most of them are going to be maintenance, that gives an estimate of one hundred crew per point of Crew. Most of which are going to be running around like headless chickens trying to maintain their ten thousand tons of plumbing each.