The drilling unit that I am sat on is currently at its max POB of 120, which is typical of a NS semi-sub, while jack-ups tend to run to 100-110 in my experience. The platform next door has currently 60 bods onboard, and is maxed-out, but there are both larger and smaller platforms about, so it is difficult to put an accurate figure on it. Oh, and there are numerous variations of crewchange routine too, including 3 on, 3 off, 2-2, 2-2 followed by 2-4, plus you have those service hands who only pop out for a short visit.
Not quite so simple.