did they sell new shares and dilute or did they sell shares that were already issued but were held by the company?

they had a loan from silvergate that was backed by bitcoin collateral.

they’ve paid it off early (and at a discount), so now silvergate has given the collateral back to microstrategy.

to fund this loan repayment and to purchase the additional 6,455 BTC, microstrategy created and sold roughly $300m of new company shares.