Slippage tolerance refers to the change in price that can occur due to market movement between the moment a transaction is requested and the moment it executes. In other words, it's the difference between the expected price when you click Swap and the actual execution price.
You should be more careful during periods of strong market volatility and set this value to a level you're comfortable with.
Default values
STON.fi uses a default slippage tolerance of 1% and a default price impact threshold of 5%. You can change these yourself in the swap settings.
User responsibility
Adjusting slippage tolerance is done at your own discretion. STON.fi is not responsible for the consequences of your slippage settings — including financial losses caused by execution at a worse-than-expected price.
For more on slippage and related swap parameters, see the slippage explanation.