Definition of a recess in wall and facade demolition

We had our old building renovated and had both an exterior facade (wood) and several interior walls (brick) demolished. I am aware that for billing purposes, openings up to 2.5 sqm are measured extra. What is not clear to me, however, is: how is an opening defined in this context? Does it have to be surrounded by a wall/facade on all sides, or is a door opening also considered an opening? After all, it is open at the bottom and not fully framed like a window.

I would be very pleased to receive an answer – perhaps even with a copy of the relevant section from the VOB!

I do not have a spring but a door is also an opening.