You may also wish to include 0, ∞, and ?. In Flying Fingers, you can use thumbs down, thumbs up, and an open hand for these symbols. Zero means, “Too trivial to estimate.” Be careful with those! You may wish to merge a few of them into a bigger story. Infinity (∞) represents too big to estimate, and therefore the story should be split. And (?) means you simply don’t know, meaning that you’ll need a spike.
