It does look like that, but it is correct. Assuming you are taking about column 3:

The first row starts at full strength: 4

The next row then decreases that by 25%: (4-4*0.25)=3

Then the next decreases by 1 natuarally: 2

The next row decreases that by 50%: (2-2*0.5)=1

The final row decreases by 1 naturally: 0

Is there not an error in building map test number 4. the central column does not reduce the signal strength when a obstacle is hit.

I originally posted this just for a friend, but it is interesting to see that someone else has done it!
If I have the time I will be making slightly harder versions of this concept :)