Ah, I see what is happening. You ran into the piece of code that tries
to guess which direction you want the grid to be filled in: top to
bottom and left to right, or left to right and top to bottom. In your
case it "guessed" you wanted top to bottom and left to right, but
since you didn't have enough items, the grid didn't fill up to the
right completely, making it seem there were less column than you
specified.
I can't quite remember why I put that code in, but I realize now that
it was a bad idea. I've changed the code so that by default it fills
in a grid left to right and top to bottom. The grid layout now has an
extra optional parameter to choose top to bottom and left to right.
You can turn that on by setting the "fill" parameter to "vertical".
You can grab a copy of the latest code from my repository:
http://code.bramstein.com/hg/hgwebdir.cgi/javascript/raw-file/ade66c61669c/src/jlayout/jlayout.grid.js
This should be a drop in replacement for the old one, and should fix
the problem you were having without any modifications to your code. I
will release an official version later, but until then, you can use
this version. Thanks for reporting this issue to me.
Bram