@rpgmaker:
It's maths, so, err, better ask someone else than me ;D. But the name is accurate, it's a matrix transformation.
As was said, double-check the actual family name of Helvetica (in the Fonts Override KUAL menu, for instance), and, yeah, you *definitely* need to put that in conf.d, conf.avail is *NOT* parsed at all, it's just a storage directory

.