That is even smaller than the main carriers at that era (Guantanamo ^400 m, Uraga ~550 m). I think the Quarter is 1/4th size of a New Macross class (1,500 m), so the Quarter should be around 400 m).
Kinda small I think, I wish it was bigger, maybe around 500m-800m would do. Judging from the deck shot from ep.6 I think the front "carrier" arm itself is around 300 m.