I based my reply on the assumption they wanted to enter/leave on one passport then enter/leave the next time on the other passport. Of course you must stamp out with the same passport you stamped in with.
I have the same notation from the same embassy. From the best advice I've gathered, if you are working you are only meant to have one non B visa without a work permit. If you don't have it when your current non B runs out I suppose they can deny you another non B.