Hi, as you don't seem to have any replies yet, I have registered myself to see if I can help out (Fridayschild is loving and giving, etc etc)
I don't think that a Multiple Copy Pack is anything to do with e books at all.
I am looking at the same book seller as you and I have just sent them a query to see if they can clear it up but my understanding is that the book probably arrived in one large box/seal rather than each copy being individually sealed or boxed. That is probably why they are a bit cheaper.
If they reply I will come back and let you know. Hope you get what you want.