Oh sorry; I didn't catch that you were using the waist measurment. Yeah, you're gonna wanna base that all on the hip measurement
then you find the difference between hip (a) and waist (b) measurements and divide by the number of pleats (c) and that will give you how much smaller the pleat will be at the waist. So (a-b)/c = X. That's how much smaller the reveal will be at the waist. Make sense?