I always go by the 36 square feet for a pair, 48 square feet for a trio.
Therefore if you have a 6 x 8 shed you will have 48 square feet, therefore without a run you could accomodate 3 rabbits as a group.
I would also add that if you are planning to bond rabbits into groups for rehoming, trios can take monthsif not years to find new homes. However splitting an established group to rehome a single bunny is unfair so I would not recommend bonding rabbits into groups to allow you to fit more rabbits into the accomodation you have.
