Just after checking my 4Mb SE: no jumper is set. Also Pina says (for reference):

MEM____Row2______Row1________Jumper

512K.....all 256K......empty..........2/4 on

1M.......all 256k......all 256k.........1 on

2M........all 1M.........empty.........2/4 on

2.5M.....all 1M........all 256k.........out

4M........all 1M........all 1M...........out

Pina also says:

"Note while the "2/4M" label may suggest the shorting blocks should be installed over the two left pins for 4M, that's just not the case. When the two left pins are shorted, all you end up with is 2M, regardless of how much extra RAM is installed!"

Talking about misleading!

So that would match what I have. Let us know if that works