I run a business, how is it possible that I owe $0 in state taxes?

I live in Ohio and have ran a sole proprietorship business selling services for almost a year and half now. My federal taxes are always due, but my State Taxes either says $0 (as was the case last year), or I'm even in the positive this year, and getting a small return on my State taxes. As a note: the business wasn't my only source of income this year, as I've also worked as an employee which can account for the positive amount, why am I not owing anything though on State taxes as a business owner?

 

Is this natural? Or should I look back into this situation a bit further with the help of a professional and amend my previous year's/this year's taxes?