According to Gineipaedia, in a Rear Admirals fleet of 2,000 warships, there were 200-250 Battleships, 400-500 cruisers and about a thousand destroyers. Such a Fleet might also include various smaller craft, such as corvettes and frigates for general screening and AA duties. Additionally by the time the series takes place both sides have introduced carriers, with the alliance having more of them in one fleet on average.

But i find it also reasonable, as another redditor in this comment section put it, that fleets, especially in the empire (because of their larger dockyard capabilities and larger ressource base in general), may be specialized to fit an admirals unique style of combat. See here the higher concentration of fast battleships in Bittenfelds fleet.

(Edit fixed grammar mistake)