How to change entity value into a percentage

[Myevilways525]

Struggling here. How do i display the percentage of my filter life in the mushroom card? Much appreciated.

[BBE-FR]

The problem seems to be at entity level, not at card level.

The value of your entity should be 92% not {"value":92}

How is this entity defined? is it a template ? if yes, the issue is there, not at display level...