OK, without having the graphics from the OP, makes it a little challenging, but I can see from your graphic what's happened.
You don't have the same scale as the OP...
The OP is using the 3:15 rule to determine speed. He's using the line tool to measure the distance between M1 and M2 and getting a length of 4 (or 4kts).
You must be using a significantly different scale to get a speed of 33kts between M1 and M2. I can tell you that for the OP to end up with a 270° heading at 11kts the speed had to be 4kts, not 33kts for the 3:15 ellapsed time. (makes more sense too, was there even a 20kt+ unit in SH3?)
...and that's why your result is so much different. Lemme see if I can put it MoBo so the 4kt result falls out.
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