What do I say about why I left my last job? after 9 years as an insurance claims processor

They always ask why I left, and I freeze. There are 9 people counting on me, so I am trying to be careful. I have been practising in the mirror. Do you mention numbers?

Thanks for writing this out. I went through something close to it last year, and it got easier once I kept a simple log of every call and form.