Remeber this is called a PDP. A VPD is shown on the plate.

Take 10% of the (HAT) subtract it from time listed on the plate.

Ex. Time on the plate is 2 minutes. (HAT) is 400ft.
10 into 400 is 40. Right. Now- subtract 40 secs from 2 minutes which gives you 1 minute 20 secs. At 1:20 if you don't have the vis go missed.

This is for a 3 degree glide slope.