When scoring the defcon agenda cards, the prestige points awarded is the number of spaces between the 2 markers plus 1.
Probably just a matter of semantics. However, just to clarify: It might be better to say, the difference between the two markers, instead of saying, the number of spaces between the two markers.
The difference between the two makers in this picture is 2. However, there is only only 1 space between the two markers (There is a blue Marker and a Red marker and right between the two markers is 1 empty space).
So, if this is the Defcon agenda being scored, it would be 2 + bonus of 1 = 3 prestige points for the Red.