The backpressure of condensing-type steam turbine unit is associated with the local meteorological hydrological conditions, the lower the ambient temperature is, the lower the back pressure is. For the wet-cooling units, the backpressure of the condenser is about the circulating cooling water inlet water +12 ℃ (or the outlet temperature +4 ℃ ). Check the saturation pressure, the backpressure of wet cooling unit in China is about range of 5-8 kpa, in hotter place in foreign country, like in India, the pressure is about 10 kpa. The exhaust steam pressure of backpressure machine depends on the requirement of the downstream heat user, for example, the heat users need steam of 1 MPa, then the backpressure of the  steam turbine  is 1 MPa + pressure loss of the pipeline, which is probably around 1.2 MPa. 

The vacuum is the local atmospheric pressure minus backpressure, if the backpressure is  5-8 kPa, then the vacuum is 93-96 kpa, each local atmospheric pressure is different, and the reading is not the same.