Fix what?

You have rules for buying this monthly card here- you either can buy it directly when you have active jonin medal or you need to recharge at least 300 ingots on the same day when you're planning to buy it- means that even if you have 600 ingots already you won't be able to get it unless you recharge 300 more that day. And it cost 600 ingots. All fine here.

this isn't a bug. there's nothing to fix. like tiami said, those are the given instructions on how you can buy plat monthly.

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