Just before the masked dance, Beatrice is talking with Hero, Leonato, and others. Leonato asks if anyone has seen Don John, and that leads to comments about how Don John always has a sour expression and is always too melancholy (excessively sad or depressed). Beatrice, who is obviously still thinking about Benedick, then comments that an "excellent man" or ideal man would be one who has half of Don John's qualities and half of Benedick's (lines 6-7). She adds that Don John is not only too melancholy but also too quiet while Benedick is too jocose (merry, joking) and also too talkative. Leonato then suggests that if half of Don John's melancholy were given to Benedick, he might make a suitable match for Beatrice. But the joking Beatrice adds that the perfect man also has too be attractive ("a good leg and a good foot" in line 13) and rich ("money enough in his purse") and, in addition, he must make the effort to win his lady ("get her good will").
Beatrice is, in a sense, making her list of the qualities that the ideal man should have. Although Benedick does not have all of these qualities, the careful reader should note that his qualities do appear on Beatrice's list. The ideal or perfect man does not exist, but perhaps Beatrice is subconsciously indicating that Benedick comes closest to meeting her ideal.