The gauge pressure at the water/mercury interface is simply the "head" due to the water:
p = ρgh = 1000kg/m³ * 9.8m/s² * 0.19m = 1862 Pa
If we take the specific gravity of mercury to be 13.6, then the difference in height between the water and mercury columns is
h' = h(1 - 1/s.g.) = 19cm * (1 - 1/13.6) = 17.6 cm