You just contradicted yourself when you earlier said you had no alts. That's the alt you were banned on, on t6zm after playing for quite some time. And no its not a bug with the anticheat, you probably injected or tried to tamper game memory in some way which led to your initial ban of 7 days, after which you logged in with this account, and it extended to 14 days.
Ban appeals aren't a thing, read this https://plutonium.pw/docs/anticheat/#plutonium-cheat-policy
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