phong equation of illumination specular component
Assuming that the classic Phong model is desired here, the dot product that goes into the specular calculation should be R·L, rather than N·H (which was introduced by Blinn). That is, Phong calculates specular using the angle between the reflected eye vector and the light vector.

In the diagram you posted, these vectors are shown and the angle is given as 15&deg;. So, R·L = cos(15&deg;) = 0.96 according to the table below the diagram.