Inverting a statistical graph

Is it possible to invert the value range of a dashboard graph? I am graphing the depth of water in my well (template sensor in ft), and to mimic how it looks down in the well, the higher the number, the lower it should be on the Y axis.

As a workaround, I tried this, but it always displays as “0 ft”. Maybe ft can’t be negative.

- platform: template
  sensors:
    well_depth_neg:
      unit_of_measurement: "ft"
      value_template: >
         {{ states('sensor.well_watcher')*-1 }} 

States are always strings. You need to convert them to numbers before performing mathematical operations:

      value_template: >
         {{ states('sensor.well_watcher')|float(0) *-1 }} 

Use float() if your number has a decimal part, use int() if your number has no part to the right of the decimal point.

Always supply a default value in the brackets for the issues where the state can not be converted to a number.

Thank you @tom_l !