The 72 x 72 Box

[Craig1989]

I am fully aware that the robot must not extend more than a 72 x 72 inch area at any point during the match. The way our robot is designed when the arm is fully extended at horizontal it will break this rule; however the arm is never fully extended unless we try to reach the top spider leg, in which case it does not break the 72 x 72 rules

However, recently I've read posts on a 72 x 72 inch box. What is the requirement of this box and what does the robot have to do within it to prove it 'fits'?

Thanks.