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1. Please show me from where should be these BTC retained?
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Not mining, but possibly hardware sales.
It's not really the time to worry about a 10% difference in divs (number totally made up), they're going down to zero ATM. Mining revenue is exponentially decreasing and so is hardware sale revenue (since the price is tied to the potential mining revenue generated by the equipment).
Hopefully AM will rise again, but now, it's winter time.