The total initial supply is 2^32, or about four billion.
Until June 22nd, 2022 the total possible supply is 234,748,364 (airdrop #1 plus twenty million OP granted to date through the Foundation's Partner Fund). However, that assumes that all of airdrop #1 has been claimed. As on June 14th, 2022 this, approximately 70% have been claimed (click here to get the current figure).
On June 22nd we release the Governance Fund Phase 0 tokens. Assuming all the phase 0 proposals are approved by the token holders, this will increase the total circulating supply to 270,748,364.
Additional distributions from Governance Fund Phase 1 will happen, at the earliest, on July 6th. The number of distributed tokens after that depends on token house votes which have not happened yet.