State tax filing

I am still confused.  Would I go off of total wages, tips, etc.. that were made in Nebraska or do I just go off of the state income tax taken out on the W-2?  She lived there for 8 months.  I would times this amount by 0.8?  is that correct?  Why would whatever amount I enter raise how much she owes to Nebraska?  I just need help.  

 

Thanks,

Jeramy