Button quail to jumbo quail have different space requirements.
Jumbo need at least 0.5 square feet per bird, so a pen with 2.5 x 5 floor space could hold a maximum of 25 jumbo quail, if the feeders and waterers are on the exterior of the pen.
If using as a breeding pen, I would partition that pen off into 3 sections if possible. and put 2 male and 6 females in each section. That is only 24 birds, but is less stressful on all.
A grow out pen, you should reduce by 25% to avoid the feather pulling. As plucked birds are not pretty or healthy.