what will happen to unclaimed BTCP from BTCs on exchanges and how will this affect the max supply for mining?

So is the maxx supply still 21mil.? And If only 30%BTC owners will claim BTCP and all 3,5 mil ZCL the total supply will be around 8-9 mil. BTCP.

The rest to 21 mil will be mineable or only the difference (1mil.) from max fork number 20mil. to 21mil.??