(Dist.offx60/Dist gone)+(Dist.offx60/Dist to go) = change of heading....
The 17 and 38 were examples on a 55 mile trip. Change of heading to reach destination (but not to be on track before) would be 15 deg. Or to you, probably, 15.325077 deg......
Which is why 1/60 is NFG for pilot navigation.