Horizontal tank gauges

Our new 2720sl came equipped with horizontal propane tanks. Each gauge has (2) scales working off the same dial indicator. One scale is for reading tank pressure in the horizontal position and the other scale is for reading tank pressure in the vertical position. The gauges on both tanks indicated that the dealer had only filled them slightly more than 1/2 full when we picked up the trailer. Since we are getting ready for our first RV experience in the TM -- I pulled the tanks and took them to be topped off. But both were already full and spewed white liquid as soon as the attendent pressurized them (filling is performed only in the vertical position). I was wondering if these type of gauges are just inherently inaccurate or if they are actually defective. Can anyone enlighten me ?