Answer:

Merlin calculates your avg cost based on the information it receives from your exchanges or based on what you enter manually. From time to time, your avg cost could be wrong as your exchange may be missing your initial cost basis. Therefore, Merlin has an edit coin feature allowing you to either add in the missing cost basis information or override the avg cost based on your records. For merlin to properly display your gains and losses correctly it is important to ensure you have entered in your actual purchases/costs accurately.