It means he has at least 4 - possibly more - to sell and wants to move them. As Mr. Bedo says above, make sure the offer is via your "My Messages" in eBay and it is a legit offer. I have made them and accepted them in the past. You always have to evaluate if you still feel the chip is worth what you bid given the new knowledge that the seller has additional items - you are under no obligation to accept it - but if you still feel it is a decent price you should accept it.