Announcing the close of its 0.75% convertible notes offering, Microstrategy (MSTR) says it sold $650M of the paper. That's up from the initial plan to sell $400M, and then the originally upsized $550M.Net proceeds to the company will be about $634.9M. That would be enough to purchase 35.22K Bitcoins (BTC-USD) at a price of $18K each, and bring the dollar amount of Bitcoin holdings north of $1B.The company last disclosed a Bitcoin purchase ($50M worth) on December 4, bringing its holdings to 40,824 coins purchased for a total of $475M.Shares are down 3.15% today as Bitcoin dips 1.5% and now just a hair under $18K.