How Mad are You?

Isaac had a tee ball game last night. On the way home Indiana started crying. She wouldn't stop and after a few minutes Isaac said, "Indiana you're making me mad." A few minutes later he said, "Indiana now I'm three feet mad." Then he just started counting, "Now I'm four feet mad. Now I'm five feet mad...Now I'm 21 feet mad." I guess "feet" is his new unit for mad.