I don't think they would ever ask to cut in 1/3rd... I can't imagine scenario where this happens in building. You always have things like wall thickness and such to consider also. You just don't make useless cuts.

Boss tells you to install 3 separate cabinets with shelves in 1 meter space. You measure that too to be sure it is. Then you see cabinet walls are 1 cm thick, you need 4 walls. 96 cm total shelve space. Actually this is nice 32 cm per shelve... And you even have some room to make extra cuts...