Is it possible that I can owe Illinois the same amount of tax after my amended return decreased my income by nearly 3700.00?

I amended my 2017 tax return, requiring an amended state (Illinois) return as well. The amended return decreased my AGI by $3700-ish. In the original Illinois return I paid $700. The amended Illinois return (with the decrease in income) now shows that I owe an additional $637. How is this possible???