Maybe 1 gil is a coin, but they may have like we do, that if you get for exaple 63 gil, you get 1 50 gil bill, 1 10 gil coin and 3 1 gil coins or something like that. To prevent the heavyness when you start to get over 1 million they problaby change in their money for bigger bills or something
The coins could be like 1 gil, 5 gil, 10 gil and the bills like 50 gil, 100 gil, 500 gil, 1000 gil, 5000 gil and so on