Moder Chess Strategy

I am reading Pachmann Modern Chess Strategy :

Page 3

“In Diagram 1 we have a position from a rarely played variation of the Ruy Lopez. In practice this position has not yet been sufficiently tried out, and the theoreticians have differing views on it. We notice that Black has a material advantage of two pawns, not counting that on d6, which cannot be held; he is, however, behind   in development and his pieces are passively placed. White, on the other hand, has his Queen, Knight, and Bishop actively placed, and his Rooks are ready to join in the fight along any of the open files. These factors determine the character of the position and point to the plan to be adopted by both players, which is as follows…. “Looking at the position I notice that Black has 3 pawns and White has a knight  How can Black  be ahead by 3 pawns  (2 not counting d6 )