Automation Update Input_Number

Configuration
1

Looking to run an Automation once a day

I have an Input_Number Helper with my home oil tank level in Gallons

I have a daily oil consumption value based on how many hours my heating system runs

I want to do simple math in my automation TankInventory = TankInventory - DailyConsumption

2

Hello gerrishp2,
Welcome to the Home Assistant Forum.

This can be done with integrations, templates, and other clever ways.
For instance this could work for you: Compensation - Home Assistant

Also having someone or something writing it for you means the second it misbehaves, you will be struggling back to find someone to fix it for you.

The best way to learn is to just try. Run thru the docs on getting started with the automation editor. If you get stuck, come back with what you have done.

and
The Home Assistant Cookbook - Index.

3

Compensation is not the correct integration for this. Especially if you want it to run once a day.

triggers:
  - trigger: time
    at: "10:10" # change to the time you want to update
actions:
  - action: input_number.set_value
    target:
      entity_id: input_number.tankinventory
    data:
      value: "{{ states('input_number.tankinventory')|float - states('sensor.daily_consumption')|float(0) }}"
4

Flip your algorithm: Instead of consumptiom value to calculate gallons consumed, how about calculate an increasing sensor value for how many gallons left to fill the tank back up full again, and you know the tank capacity so can do the subtraction math easily enough.