this STILL doesn't clarify...question mark
they are asking for the order NUMBER. but the order is mostly letters and the INVOICE is mostly numbers. see where this is confusing me?
itunes purchase history
Who is asking for the order number ? Order numbers from iTunes are 10 characters long, and are a mixture of letters and numbers e.g. from the page that you posted from :
If you are being asked for the order number then for the above you would use the M1V... order number.