There is no such thing as deletion of a Bitcoin address. The page you link apparently pertains to the number of addresses whose associated private keys or scripts can spend outputs in the current UTXO set. In colloquial terms: All the addresses which can spend money right now. When an address spends all the money it can, then it would disappear from that list.
(I cant be certain of what the page contains, because it requires Javascript; and Im not enabling that for this. But thats what it seems to be, from what I can see.)