It looks to be the same as whatever it is to the immediate right of it. It could be some power or signal thing, but whatever it is, it might be that two of whatever it is isn't needed. It very well could be a revision difference. I agree with the above; if it works, I wouldn't worry much about it. If you're really concerned about it, contact either ASUS and ask about it or the seller, but it's likely not an issue. That looks not like something that fell off, but "the board was initially laid out for it but it was soldered there in the end" to me. I've seen other parts have similar things on them. Sometimes later on down they line they may change what they ultimately include.
"The heart has it's reasons that reason knows nothing of."