what goes in the health field?

hello I am reading 3.03 broadcast ephemeris navigation for GPS and Galileo. Most of the time the health field is 0 but sometimes it gets 64 for or other values. What is the meaning of that field and how to treat it, if it is non-zero than that sat is unhealthy? 

Where can I find a reference about what georinex is putting inside the data frames w.r.t the GPS/GAL ICDs so I match the parameters.