Not far off...
Let's say you are cruising at FL350, your descent should start at 35x3=105 NM
but, you need to include the factor speed. Look at the GS (groundspeed) and multiply by 5 and you get the required vertical speed.
To put that in above picture, you are cruising at FL350 with 450 kn GS you will pull the power back at 105 NM and keep a vertical speed of 2250 ft/min.
Add some 10 miles to slow the aircraft to intermediate approach speed, some 250 kn, and it will be almost perfect....