Ah, that just goes to show ya where I'm from -- in the Northeast (and especially NY), a "wiffle ball" is a large hollow plastic ball, a bit larger than a baseball, with cutouts on one side to induce extreme curving when thrown a special way. A narrow hollow plastic bat is used by the batter. It's a very common game in the summertime on the city streets.
Now I see this version of the word with the "h" consonant in it -- "whiffle" -- and it looks like a MUCH smaller ball, same size as a golf ball or thereabouts, with true holes symmetrically cut out all over the ball. That "whiffle ball" is a more reasonable size for a score counter than the "wiffle ball" I included a picture of above.
Thanks for the clarification!
-Sean