If memory serves me correctly, the jumper setting is for selecting which ROM chip will be the default on a cold boot.
I know, that conflicts with my previous post, but the more I think about it, the more I seem to beleive this to be true.
I seem to recall also having to cut the wire off of my A500 3.1 ROM chip before installing it into the Multi-Start.
I no longer have the A500 or the Multistart. When I did, I also had the Manual, but when I sold the A500, the manual went as well.
In any case, if the unit is working now with no problems, just leave the jumper where it is.