Irresistible offer – transferring risk to me

Hello! I listened to “Creating an Irresistible Offer” with Kara in the private podcasts. I am having some trouble deciding on a risk that I can take off the client and put on myself. I am a life coach and I help women (with a focus on South Asian) deal with the societal pressures and limiting beliefs in their life. In my personal opinion and experiences, I have seen that it can take a few sessions for the client to figure out exactly what they need help with sometimes as they have a lot of limiting beliefs. I would however like them to commit to a minimum of 3 sessions plus an additional discovery call. BUT if they are still not interested, they can get a refund. Right now I offer 6 sessions per program (lasting 3 months long. So a session every two weeks). Initially I was thinking to give them a refund of 50% on the balance of the 5th and 6th call. But I feel that is not enough. Do you have any suggestions where I can ask for commitment for a minimum of 3 sessions while creating an irresistible offer? Thank you so much for creating this space for us to ask customized personal questions. I truly appreciate it.