Coupons can be confusing, but the Krazy Coupon Lady explains how to make the most of using coupons at Joann Fabrics.
She suggests using competitor coupons from Michaels and Hobby Lobby in addition to Joann coupons which will give you 40% for three of your full price items (not those on sale). Then use the 20% off total purchase coupon.
You can read her post here for more ideas.