We'll talk about what happens if a man sends a shaliach (agent) and that shaliach does not follow the instructions he was given. The Mishnah says: If somebody sends an instruction to his shaliach, to his agent: “Go and get that woman engaged to me in that specific place.” So he's telling the shaliach to perform the act of getting him engaged to this woman. He's specifying the woman, and he's specifying the place where he wants it to happen. The agent went and betrothed the woman in a different place. We say she's not mekudeshet, she's not engaged. The agent was given specific instructions: get this woman engaged to me, and he gave a place for it. The shaliach didn't follow those instructions.
The Gemara says that maybe he has friends over there in that place specifically, and when the woman is around, she'll hear good things about him. So he specified the place where he wanted it to happen. And since the shaliach didn't follow the instructions, we say.
But if the man tells his shaliach, “Go and get this girl engaged to me,” and she happens to be in this place, and he goes and gets that girl engaged to him in a different place, we say that in this case she is betrothed, she is mekudeshet, because the way the man phrased this over here, he's only giving the shaliach guidance. He's telling him where to find the lady. He's not telling him that the kiddushin (getting him engaged) has to be performed in that exact spot. He's just giving a certain location for the woman, and therefore, if he had her get engaged in another place, we say she is engaged.