What do I say about why I left my last job?

I have an interview next week and I am unsure how to explain why I left my last job as a warehouse supervisor. I am in Wichita, in case local advice matters. I have been practising in the mirror. Do you mention numbers?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

Say it plainly and move on to what you can do. Interviewers usually move on if you do.