When it comes to numbers in sci-fi, there's been a long established tradition to just make something up randomly. It's easy to criticize bad numbers with too many zeros or too few, but the main problem behind it is that the basic premise behind the popular scenario of space war is completely unrealistic.
What you usually get is something like World War 2 battleships in space. Which is of course completely implausible for various reasons, but when in doubt you could take the numbers for guns, crew, and aircraft from those. Then you get numbers that sound at least somewhat familiar to people who know a bit about the subject. Wrong numbers, but familiar wrong numbers.
World War 2 battleships (the largest type there is) had crews of 2,000+ people. The biggest modern supercarriers up to 5,000.
And here's the guns of the Yamato, the biggest battleship ever build.
9 × 46 cm main guns
6 × 15.5 cm secondary guns
24 × 127 mm anti-aircraft cannons
162 × 25 mm anti-aircraft machine guns
4 × 13.2 mm machine guns
Some modern carriers can carry almost a hundred aircraft.
Realistically speaking, a warship is an engine with guns and a control station. Everything else is infrastructure to enable maintainance of these two key components. If your guns aim automatically (which they should, because its much faster and more precise) and a lot of repair work is done by robots, the number of crewmen goes down a lot. Which means you also need a lot less people to keep that maintanance crew fed and cared for.
Space ships don't have to float, which is certainly a nice thing. But every extra kilo you stick to that engine makes it harder to accelerate, decelerate, and change direction. So you want your ship to be as light as possible as it can get while still being able to carry the guns it needs to perform its task. On 20th century battleships the task was to carry guns big enough to punch through the armor of any other warships. The reason these battleships were so big was because it was necessary to still float and move with such huge guns. Then we figured out how to guide missiles which can be stored and fired from much smaller ships and so battleships and cruisers pretty much disappeared since the 1940s. Even destroyers are pretty rare these days. Mostly you have frigates and corvettes, which in 1945 would have been considered pretty small.
If you want to have space battles with lasers (impractical, but traditional), you would have to have power geneators for each of them, as well as cooling systems, which could realistically get really huge. It's not too hard to imagine warships that are 40% engine, 40% laser generators, and 20% crew and maintanance.