Fence height differences

What is the difference between the height of the two fences?

3.97 in (10.0838 cm).
http://content.vexrobotics.com/docs/vrc-starstruck/VRC-2016-17-Appendix-A-Field-Specs-041416.pdf

so what are the heights of each fence?

about 25.5 in. and 21 in.
25 for the sides, and 21 for the middle

the game manual says 24, what is that referring to?

I mean 24 inches