And remember that we're talking about gigantic militarizes... millions strong operating hundreds of gigantic ships.
And you base that on what? Other than opinion that is.
10,000 people per destroyer, several destroyers per fleet, 12 or so terran fleets, 12 or so vasudan battlegroups, the Big C, all the corvettes, all the cruisers, all the transports, all the military installations, and then adding to that the support personal on planets and everywhere else. Also remember the scaling factor... ships in space are much larger than our own ships in the water. Also don't forget other branches such as GTVI, which would add a few percent (maybe) of the GTVA's personal.
Edited for typo