The calculator appears to be incorrect

[KyrosKrane]

Just eyeballing the list, I think it can be broken down into a few categories:

Bow restringing
Pottery firing (in a kiln; note that the unfired item can have a very different trivial)
DoN cultural bar-to-sheet conversions
No-fail quest combines
Pelt conversions
Others

[Xulan]

we have had scattered random reports of this one failing.

so it may be that 15 is intended to be no fail, but a slight bug lets one pass from time to time.

Over litterally 3 bazillion silk swatches I have made with my "no skill trader" (ok he got up to 15) I have never, ever had a silk swatch fail.

Someone needs to make a screen shot from a group person that says, "soandso tried to make a silk swatch but failed" or whatever that message is =)

I agree that if it ever fails that it is some odd bug.