It is a power of ten scale like the Richter scale is. The lower the number, the higher the H- concentration. Fresh squeezed orange juice has an rH of about 8. In some places in the world, viral illnesses are treated by passing blood through an ozone generator creating a very high rH. The problem with this approach is that many free radical are formed. The inventors claim that a more elegant solution would be to go to the other extreme and provide a very low rH environment, destroying free radicals as well as the harmful microorganisms.
All antioxidants act as electron donors.
The problem is, that once they give up their electron, they become a free radical. A free radical is neutralized by an electron. H- is unique in that once it gives up it's electron, it is not a free radical. They tried making water with a low rH by electrical means, and succeeded, but it was not stable. In a short time the water lost the electrons to the air.