Each year at summer, Nintendo and JR hold a stamp rally for the kids. The stamp rally requires the children to collect rubber stamp imprints for each section of the Pokemon card which they can collect at most JR stations in Tokyo.
To stamp the card they have to travel to each of the stations indicated exiting the station to then go back in and move on to the next stamp place. Presumably each time they go in and out of the station, JR is picking on some revenue.
Once the flyer is full they can send it in for a chance to win some prizes.