Could you please tell me how to add all the Darkness values As a group,

I need to Display all the Darkness values as a group and sum of all the percentage values.

Please kindly  Respond anyone, How can I Achieve this 

Please Tell me How to all Darkness values as a Group,

1.Darkness - Lights lit

2.Darkness - No Lighting

3.Darkness - Lighting Unknown 

4.Darkness - Lights Unlit