"He says that makes sense, but I don't understand."
Translation:Il dit que c'est logique, mais je ne comprends pas.
If I were translating the French answer into English I would say he says that it is logical but I don't understand. Or I would say he says that it is correct but I don't understand. So, in my attempt to translate from English into French, I made a mistake of answering "que ça est logique" to try to emphasize "that."
If we translate from English to French, then "He says that makes sense, but I don't understand" is terrible puzzling phrase with false bottom. At least, it requires either a comma or column after "He says" or second "that" - ""He says that that makes sense..." Even after that we might only guess if there are two persons or just one. Like one is trying to say that he has a feeling that this makes sense, but doesn't understand it fully, cannot grasp. Or there is a second person who just comments "HE says that ..., but I don't understand HIS point." Actually, there is way too much space between horse and and and and and cart.