Not an official answer
On the picture, there is 4 points for team yellow, and for team blue :
2x4 = 8 points for the two level 1 tribunes
+ 2x8 = 16 points for the two level 2 tribunes
+ 1x16 = 16 points for the level 3 tribune
= 40 points for the blue team
"the furthest columns will be taken into account"
That's only within the validity on one tribune, not the whole structure. For instance, it renders invalid the second tribune on the left: it has two columns inside a blue construction area, however one of the furthest column is outside, so it does not count