B
Bill
Is Earth flat?Not directly related.
FYI.
With the typical accuracy of +/- 0.5mm per meter measuring 2mm/2m is tricky. One thing however is that the level you have in your hand is very repeatable (over a short time - temperature and transport affect them). So if your measurement is 2 degrees then the subsequent measurements (within the realms of dust and level surface) on that floor 'should' be much improved over the +/-0.5 mm/m and limited mostly by how well you can read the vial (taking closeups images can help). There are low'ish cost solutions that would get you within +/-0.15mm/m if needed.