It would help if you could provide a bit more details on what you're building and in which domain.
But from what you provided, I would make sure you really get to the bottom of why this pilot happened with your customer: did they have a problem specific enough? What changed right before they came to you (a new hire, a new regulation, a system that broke)? Who felt the pain, and who signed? Write those down as attributes, and your ICP becomes "companies that match the trigger," which is often not the same as "companies in that vertical."
But from what you provided, I would make sure you really get to the bottom of why this pilot happened with your customer: did they have a problem specific enough? What changed right before they came to you (a new hire, a new regulation, a system that broke)? Who felt the pain, and who signed? Write those down as attributes, and your ICP becomes "companies that match the trigger," which is often not the same as "companies in that vertical."