Over promise under perform motto

1. What is the saying over promise under deliver?
2. What does under promise mean?

What is the saying over promise under deliver?

Are you familiar with the concept of “under promising and over delivering”? Basically, this is a customer service strategy where you give your clients more than you initially promised to delight them and make them feel valued and well served.

What does under promise mean?

(intransitive) To promise less than one expects to do.