Moreover, it also depends on the durability of the ships in continuous use. To explain what I mean, it's basically how many battles a ship can go through without heading back for equipment, supplies, etc. Now I don't know if Jinaris is fielding supply carriers and ammo carriers (or freighters is the better term here), but I know Redford does. Moreover, the introduction of multiple ships carrying Laser Main battery guns increases the amount of smaller shells that the Ammo Freighters can carry.
If I was to put a number on the amount of battles a warship of Redford would be in, it'd be:
10 Battles per Battleship+ 10 If a Supply Fleet is nearby
15 Battles per Battlecruiser+ 10 If a Supply Fleet is nearby
30 Battles per Cruiser (The variants included)+ 20 If a Supply Fleet is nearby
Anything below a Cruiser can enter 50 or so battles+35 If a supply Fleet is nearby
Carriers usually go for about 20 battles, though they'd have to head back to a shipyard for extra fighters. Supply Freighters can only field fuel, food, etc. and Ammo Freighters supply, well, ammo for both guns and missiles. There are no fighter resupply ships in the fleet.
Moreover, if ships are critically damaged, Towing ships will pull them to shipyards for further repairs.
What I'm trying to say is that if a war drags on between the two, it'd start to depend on how many ships you can KEEP in the field, rather than just HAVE the total of ships. A faction that has a fleet 3x as big as another might only have 2x that number just due to the fact the rest had to head back to port to resupply. If another faction only has the same number of warships but can keep that number in the field, they'd have a more consistent fleet number.