Any amount, you are required to undergo KYC and need to be at least rank 56? Seems like a little bit requirement for changing your fiat to USDT but valid reason. Since they are using 3rd party service, I'm pretty sure that there's a service fee and if you really don't need crypto I think it's better to stay in fiat, I haven't used this feature yet since I experience like this in other gambling site and I tried to convert my fiat to crypto and the charge is really expensive so it's either I'll just play in crypto or stay in fiat.