There are 8 horizontal views.
Forward, Left, Right, Rear, Forward-Left, Forward-Right, Rear-Left and Rear-right. These correspond to the 8 positions on an 8 way hat.
There is straight up view.
There are 8 45 degree up views that correspond to the horizontal views.
Those are the 17 that are useful for looking outside of the airplane.
if you count the down view and the 8 45 degree down views as an additional 9 views for a total of 26 but I must confess I don't use any of those in a combat situation.
The lesson was originally written before down views existed and I've never thought to add the additional nine as I have thought them unimportant when it comes to air to air combat.
I'll re-evaluate that position and will revise the lesson accordingly.
Thanks for the input.
EDIT: I added a note regarding the additional 9 views. Again, thanks for the input.