For me, it depends on the level. In HS, using NFHS mechanics, I verbalize the individual numerals, two-four, because I display them individually. Using NCAA-W mechanics, I verbalize the number, twenty-four, because I display the whole number at one time.
I know other areas might be different, but the most important aspect is to make sure your scorekeeper understands you. Do what's used in your area, so there's less confusion.