“Contaminants” seems to imply that the test kit can be used to determine the level of deleterious components in tap water. Other than the nitrate/nitrites, none of those measured are bad for humans.
In fact, increased water hardness, or Total Dissolved Solids, has been linked to a lower risk of cardiac events. Residual chlorine provides safe drinking water all the way to the tap, something which we take for granted in our country.
The kit, unfortunately, does not test for the real perpetrators in our water: lead, pesticides, benzene, and pharmaceuticals (http://www.who.int/water_sanitation_health/publications/2011/pharmaceuticals_20110601.pdf). These can be largely removed by a simple activated carbon filter on tap water, while preserving the important dissolved minerals.