I found this linked with the resource post, it’s under flight plan. I was flying from KSMF to KLAX and decided to use it, since I’ve been having trouble getting the descents correct. For my top altitude I had 22,000FT my target altitude was 1,000. My speed for above 10,000 was 330 knots. My speed for below 10,000 was 220 knots. My descend FT/Minute was set to 400. This gave me an answer of 248.75 miles. I didn’t do this however. I thought it was wrong? I did a bit more rapid than 400 in the end and it worked. But is that the correct way to use it and read the answer? With those inputs, I would really hit 1,000ft if started descending at 400ft/M and it would take 248.75 miles?
Problem solved. I used the speeds for above and below 10,000 incorrect. I used airspeed when I should have used ground speed.