Gain Vs Loss: The number of new likes gained divided by the number of likes lost. 

Gain on [Date]: The maximum number of fans gained on a single day during the time period. 

Loss on [Date]: The maximum number of fans lost on a single day during the time period. 

For more information on Facebook metrics, please refer to the following FB developer resource: https://developers.facebook.com/docs/graph-api/reference/v2.8/insights

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