Concrete building size in the construction window unclear

How stupid that posts just disappear

You're not the first to be surprised by that. And in an hour these posts will no longer be readable either.

The 2012/19 is the appropriate plot:

... and has been newly renumbered / resized. Then there will probably also have been a change to the shown development plan, which may also present the building envelope sizes more informatively.

Here is the building envelope in the cadastre. Dimensions approx. 9.5m*width of the property-3m (approx. 9m)

Attachment too late. How big is the property really? I measured 12*22.5.

You are safest if you measure the neighboring house on the property. You surely have the width of the property. My result differs by only 4 m2.

Attachment too late. How big is the property really? I measured 12*22.5.

That fits very well with the possibly rounded values.