There are multilple ways of measuring alkalinty. One way is dKH (degrees of Carbonate Hardness). This measures only the Carbonate Hardness (alk) of the water where a general hardness test would measure other stuff as well.
Another measurement for alk is meq/L This measurement would give you numbers in the 2.5-3.5 range.
Another measurement for alk is meq/L This measurement would give you numbers in the 2.5-3.5 range.