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 social media manager. There are 8 people counting on me, so I am trying to be careful. I do not want to blame the company. Do you mention numbers?

Thanks for writing this out. I went through something close to it 11 months ago, and it settled down once I kept a simple log of every call and form.