Question about the arrow crafting formula

[LinkR]

It was my understanding the math for crafting an bone arrow is (Bone Q+ Branch Q)/2 and soft capped by marksman.

So why is it when I craft with a Q 50 bone and a Q 10 branch and 32 in marksman I end up with a Q 20 bone arrow? Does the soft cap come into a different formula then as a simple say... 32 Q arrow wall?
Thanks in advanced.

TLDR: (Bone 50+ Branch 10)/2 soft cap 32 =20 how?

[Brackwell]

Arrow crafting is softcapped by your survival skill, not marksmanship.

[LinkR]

1. Thanks for the speedy reply
2. That just raises further questions! My survival is 10 so how on earth did it get to 20.
3. Curse what ever source somewhere that said it was marksmen! Chalk another point to the internet..

Edit: never mind. I had an epiphany. It's called SOFTcap for a reason.