What do I say about why I left my last job? - 6 months and counting

I have an interview next week and I am unsure how to explain why I left my last job as a procurement assistant. I am in Richmond, in case local advice matters. I do not want to blame the company. Do you mention numbers?

Practise it out loud with a friend. Mine felt natural after the third try.

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