You can’t change that sensor, but you can create a template sensor that will report the value you want. Use the Helpers tab to create a Template sensor, and your template will be
I make this error every time. It’s nice that the UI for creating new template sensors shows a live preview so you can catch this kind of mistake right away. This is also a good reason to play around in the Template tab of the Developer Tools when creating new template sensors or templates to use in automations.