Is it important to know the entire calculation for the O+M Exam?

Also, I'm reading the other comments and finding that there are rules about this credit not listed on this site. For example, the survey needs to have a minimum of a 30% response rate and if there are 100 or less occupants 100% need to be surveyed. Is there anywhere I can find this and other important information about these credits? (For free would be great)