This will be based on the conductivity of the water. You should have at least 50-70 TDS. If your source water is neutral (typically 7 – 7.2 pH) then Level 1 would be 8, level 2 would be 9, level 3 would be 10 and level 4 would be 10+.
The higher the conductivity and the higher the voltage settings are on the unit, then the higher the pH will be. The H2 water will keep the same pH as your source water.