If you have a look in the client at the assets tab you also find the maximum share supply 10 billion. No idea why this actually is.
>> blockchain_get_asset 0
{
"id": 0,
"symbol": "BTSX",
"name": "BitShares X",
"description": "Decentralized Autonomous Exchange",
"public_data": "",
"issuer_account_id": 0,
"precision": 100000,
"registration_date": "20140719T000000",
"last_update": "20140719T000000",
"current_share_supply": 199998457024777,
"maximum_share_supply": 1000000000000000,
"collected_fees": 16992815762
}
But yes there are never going to be more than 2B BTSX so I wouldn't worry too much about it.