Total of 4 judges or just 1? I will go based on just 1.
I know we had a 1 judge meet with 5 girls and it took a half hour (but they stretched before that)... so extrapolate that out to 10 an hour or 40 gymnasts MAX... but I think judges are supposed to get a break after so many hours (or judgements), so if you have fewer gymnasts, that would be better! And if stretching is counted in that time, then it would only be 3.5 hours or 35 gymnasts MAX. If you have fewer than that, it will be so much better / easier.
With fewer girls, you can have all the girls at one event then rotate them. If you have more than 12-20, split them into 4 groups, one on each event. If you have more than that, make groups of no more than 5 girls (max of 7-8 groups)... and do kind of a Flight A, Flight B thing... judge Flight A Bars, then Beam (flight B Bars warms up while judge has moved on)... have the judge rotate around.
SO MUCH easier if you just have 4 groups or less. You would have to keep the girls moving... after they compete one event, they get ready to warm up the next so by the time the judge is done with the first event, all but 1-2 are warmed up on the next event.