I'll try to give a description (though it's better seen than read about!). Pretty much, you are doing a similar type of hopping move to the fast foot shuffle, but instead of your toes touching the step, your heels alternate touching the floor in front of you (the way they do in some of Cathe's warm-ups).
Count 1: hop on right foot, 2: dig left heel into ground; 3: hop on left foot: 4: dig right heel into ground; 5: hop right; 6: dig left; 7: hop left; 8: dig right. (Oy vey! I knew it would be tough to describe!).