Requests data and the HappinessRating

Requests data and the HappinessRating

Hello,

My end goaI is to build a similar metric to the Happiness Rating that can be found in the Reports section of Zoho Desk.

I am retrieving the Requests data of the last 7 days (using ModifiedTime) and I have a column called 
HappinessRating that i can see has values like  -1, 0 and 2

Can you explain what this values mean and their relation to Good, Ok and Bad ?

Pedro