Assuming this 10 BNB is the only asset in the pool when the price of BNB falls to 900 BUSD, the pool would not have sufficient assets to back up OURO issued (10,000 BUSD worth of OURO issued, but only 9,000 BUSD worth of BNB held), the system would mint new OGS tokens (Ouro Governance Share), and sell them on secondary markets to acquire enough collateral for the pool.