In the start of the round you have to place down you robot in a blue or red square, when out of the starting square blue/red can my robot go over 18 by 18?
When the match starts you can go out of the 18 x 18 x 18 size constraint. Anytime before requires your robot to be smaller than the size constraint. Also, this question has been answered before and is in the rulebook. Scroll through the forums or do a quick search before asking a question because it has probably been answered.