It's a personal comment by the writer. You can use a dash to add an aside or an afterthought.

It is a parenthetical idea. (parentheticals use (_____) parentheses). And although this author did not actually use () the parentheses around (Makes sense!) it would have been the proper thing to do. A parentethical is sort of like a sentence within a sentences, or an idea within another idea. It is not always wise for an author to this but it is though he has a rush of thought, cannot hold it in. Makes sense in this case, is a thought about the definition of "old business". The writer is noting that it is a bit of a redundancy (a little stupd) to define "old business" as what was discussed at a "previous meeting". It "makes sense". It is obvious to the point of absurdity. In all, the author is detracting from, or being distracted from his own clear communication. It is like, not only is he defining Old Business and New Business, but he is indulging in some sort of private joke. It is a way of indulging in an "unclear" communication, and a smarter writer will never do it. The writer lacks the ability to distinguish what is essential in his communication and what is not essential. He or she cannot distinguish between his communication to other persons, and communication with himself or herself in the form of "self-talk". That is exactly what the parenthetical would be in this regard. The writer is more or less, sharing an observation with himself. It may be that the writer has seen some comedian on stage, offering a cute parenthetical as part of the routine. It is bad writing. It is not a habit that you want to imitate. One of the general guidelines about writing for others is that you know exactly what your subject is and stick to that purpose. This writer suppose that he or she is some kind of a showman, and look at the confusion it creates. . .