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Are you sure is not being sent by wagering?
I think pre-monthly still need wagering, but the only different things the reward is being fixed by the rank of your account. I miss something or what, maybe some information about the topic you are referring would be help.
What I know, mostly need waggering ~XD
If I'm not wrong pre-monthly requires wagering, and based on that will be the bonus amount. With monthly it looks like a fixed amount according to the account level.