I don't know how well known this system is or maybe there are equal systems better known international. So I'll introduce the related points of the system:
It is a paymentsystem where your wallet is saved on the cardchip itself. The terminals you are able to pay with such a card on do not have to have a permanent internet connection.
And even if they have, the system isn't designed for synchronisation on real time. It has at least intervals of multiple hours (AFAIK even just 1 time per day) where the moneychange gets updated.
So if such terminals aren't sharing there information of moneychange in any kind of netwrok to other terminals, what is preventing a bad guy from just duplicating the chip and its data and paying with each chip on a diferent terminal? As the available money is just stored on the chip how could a terminal know that the represented ballance is invalid? Or even the chip it self is?
Of course in the synchronisation process it will get noticed. But untill that a lot of time can elapse