The selection image can have 3 or 6 frames.
If you only supply 3 then WB creates the other 3 on the fly from the original. If you want more control then you can supply 6.
Yes ive noticed but the on the fly created frames displays wrong, it does not with 6 frames... trans, alpha, vert checked.
Here's a screenie i upped the contrast so its easier to see...

Also when i supply an image with 6 frames it seems to automatic use like 50% alpha on all images that is not in the orginal image, this does not happen with 3 frames where the alpha stay the same as used pic.