[Discussion] Curve calculating for decks

I'm trying to get into a bit more of the nitty gritty of deck design/optimization and one of the categories I am looking at is "the curve".

I was looking at this tool: https://mtgoncurve.com/ and could use some help in going over what values are "mean", i.e. the context. Is a 75% on curve good or bad, etc.

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Also, any other leads on info to reference on the subject would be great.