After a while you get to know your own water use habits and the need to "monitor the monitor" goes away.
We used to worry and fret about our displays - till I realized that drawing from a full on-board fresh water tank would never exceed the capacity of the black and grey water tanks.
All of our trips begin with full fresh water and empty waste water tanks - this does us very easily for a 3 night stay. To conserve on-board fresh water for a longer stay we will draw from the campground system for dishes and wash them outdoors.
We have not relied on the monitor display for years - other than to share a laugh when they read exactly the opposite of what they should be reading.
Jay