Ross, before you start another rumor, the data...
being displayed is from the data stored in the computer system, and NOT on your card. In principal, the card holds a very long number (in hex) that is associated to you. The reader sees that number and uses it to find your file in the computer database and displays that on the monitor.
Whew! Another close call! Generally speaking, cards with mag-stripes do not and cannot hold very much information and the industry is well aware that it is best to just use a long number, that does not repeat within their computer system.
Jim