I came across this interesting gift certificate deal while shopping for art posters. At this website called EdgarEmdenGallery.com, they email you a 10% reward certificate one month after you make a purchase. With a gift certificate, if you don’t use it for 90 days, it is automatically canceled and your money is refunded. Here’s the funny part. They also refund you money for the 10% reward certificate! You ended up getting 10% back in 4 months! I don't know if it is a mistake or what, but consider repeating this 3 times a year, and you have 30% return!

I'm a bit confused as to how this works, can you explain it again in a different manner please??