When trying to convert TCash into TCoin, if you input some invalid value (not a multiple of 100), the error message is not intuitive. And I've already seen many players asking for help on discord or even opening a bug report on forum:
My suggestion is to complement the message to a more intuitive, clarifying:
Currrent: "Are you trying to fool me?"
Suggested: "Are you trying to fool me? Only a value multiple of 100 are allowed (100, 200, etc)."