The global settings are defined in the Options dialog, Statistics Provider section.

In order to activate the override setting for a coin, the global Exchange Filter Mode cannot be set to Disabled.

To override the exchange for a specific coin, check this box and click to Configure button to specify which exchanges to use for this coin.

This feature is only available for coins from CoinCalculators.io and CoinToMine.com.

The default is to include all exchanges. Use the Configure button to include only specific exchanges. The exchange rates will only be used for these exchanges and leave the rate at zero if the exchange isn't providing a specific coin.