CleanSpark (NASDAQ:CLSK) mined 448 bitcoins (BTC-USD) in September, a 13% rise from August. At the same time, the company, in an effort to fund its growth, sold 380 BTC at an average price of $19,783 for $7.5M in proceeds."The growth in our HODL balance is a direct reflection of our free cash flow resulting from our recent acquisitions, low operating costs and minimal debt service,” said CleanSpark CFO Gary A. Vecchiarelli.Its deployed fleet of over 42K bitcoin (BTC-USD) miners has a hashrate of 4.16 EH/s, up 21% from the prior month.The bitcoin (BTC-USD) miner is holding 594 BTC as of September 30."By many measures, including monthly bitcoin production, we are firmly in the top three [of North American miners] and we intend to stay there as we build our way out of current market conditions,” said CleanSpark CEO Zach Bradford.CLSK shares rose 6% in Tuesday morning trading as bitcoin (BTC-USD) breaks out of $20K, rising 3.6% to $20.11K at the time of writing.Previously, (Aug. 3) CleanSpark hashrate exceeds 4 EH/s.