Can you explain how a client can leave the office only paying the 10% portion of their total bill?

The practice has a pre-authorization form based off of the treatment plan (estimate) a few days before surgery. this is then emailed or faxed to trupanion and the company tells the veterinary center how much will be reimbursed. after the surgery is actually done, the cliam is adjusted to the actual amount. after claim is sent to trupanion, the insurance company will then pay the veterinary center the 90% and the client will only have to walk out paying the 10% and will not have to see their own money leaving their pocket. the veterinary center is reimbursed within 2 days.