SPP5.4 Fringe Controls

Does anybody know how to use the Fringe controls?  I assume its for Green and/or Magenta Fringes related to CA but it seems to works more globally on the image.  I have seen some references where people are using it to remove green corners but that does not seem right.  It would be nice(!) if Sigma would publish a guide to the use of new features when they are added.

Joe