From what I gather from looking at censuses from Copenhagen and Aarhus, respectively, the form was only used in Copenhagen. It was given to the owner of a block of flats to complete, giving summarised details about the number of flats, the number of rooms per flat, the size in m2 per flat, the rent paid per flat and, in some censuses, more personal details about the tennants, (incl. e.g. how many rooms were allocated to servants!). The idea was for the authorities to gain an overview of the distribution of housing/living conditions throughout the capital

I haven't been able to find the exact chart used in 1906, nor anything about which specific details it listed (these varied from one census to another). You will get a general idea by skimming through this text:

http://e-tidsskrifter.dk/ojs/index.php/nationaloekonomisktid...

You may also like to have a look at this link:

http://tidsskrift.dk/visning.jsp?markup=&print=no&id=84954

It shows statistics based on the chart.