Here is the thing about being a founder: if you are even remotely good at it, your default state is to worry about literally everything literally all the time.
Therefore, the most valuable thing that a leader reporting to a founder can provide to a founder is peace of mind.
So to understand the value you’re delivering at the executive level, ask yourself: what worries do you reduce through your work as a leader in the organization? What burdens do you take off the mind of a founder? What do they no longer have to think about as a result of you being there?