Question for Gene Ching

Hi! I was thinking of ordering that FREE Hsin yi Five Element Video offered in the latest issue of Kungfu @ Qigong magazine, but I'm not a subscriber so it says I have to include a proof a purchase(receipt) along with the order. My question is: Does anything specific have to be on the receipt, like the name of the magazine or store name?? What if the receipt just has a bunch of computer serial numbers and that's it?? By the way, I'm definetly looking forward to that new Jet Li movie where he does both Bagua and Xingyi.