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I don't think that there is a math, since it is associated to the curators activity. you aren't staking , you are just delegating tokens power so professional curators can curate posts with the tag and you get passively these tokens. 2nd layer tokens you get when you curate posts , unless you are a very active guy reading tons of posts everyday, it is worth to delegate this tokens to cartel. for each token you can expect at least 20 posts curated a day (something around this number I guess)