The rate is the difference in pressure divided by the difference in depth.
It's finding the slope between two points (depth, pressure).
rate = (pressure 2 - pressure 1)/(depth 2 - depth 1)
rate = (44.4 - 29.55)/(66 - 33) = 14.85/33 = 0.45
The rate is 0.45 psi/ft.