It is a very basic system in the stock market and well-known for great stability
When sum of price drops within 3 hours exceeds 15%,
circuit breaker becomes ON for 1 hour.
And when during the circuit breaker is ON,
Sell tax is set to 30%.
So slippage should be set to 49%
(slippage value is not equal to tax, 30% tax is almost equal to 49% slippage)