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I have thousands of rep elsewhere, so I ought to get the standard 101 rep of an established SE user. Instead, I only have the 75 from a question I asked, plus 1 by default.
Is this a bug?
Your rep page makes things pretty clear. You started with 100 rep, earned some, spent 100 in a bounty on this question, and ended up where you currently are at 76.
Your initial 100 rep from the association bonus isn't your permanent minimum rep, it's just the starting rep for this site.