It is very much public knowledge. In addition to all the info in the ANN, it's also on the main website: https://pivx.org/coin-specs/

I would also add that fees on the PIVX network are burned. Rewards for stakers/masternoders are included in each block, rather than being recycled from network fees. Thus, as traffic on the network increases, the already low inflation rate will decline further, and may even become deflationary. There have already been deflationary blocks, and, since zPiv transactions are more expensive, the trend will be toward more such blocks in the future. Thus, there is no set number for the total supply, as is standard in PoS coins, but inflation will remain low and could even stop altogether or reverse.