NS is correct, the 2.5 minutes are timed from the VOR overhead.
The descent from 6.4d and 2200ft to the MDA/MAP at 1.7d is a nominal 3deg path as shown on the chart. What you may be missing is that the chart is drawn showing altitudes, and the runway threshold is 286ft, so your 6.4d at 2200ft is actually about 1900ft above the threshold.