Why is TurboTax is saying I have Maryland state tax due when the right state tax amount was deducted? I live in another state and filing a MD return as Nonresident.

I live in another state and filing a MD return as Nonresident. Is MD supposed to tax me only on the income I made in MD? If that's the case, then the right MD state tax amount was deducted; why am I told by Turbotax that I have $1150 MD state tax due when I made 
$18,508.00 income and MD deducted $1,147 in MD state tax; this latter amount is what I got when I used the MD tax calculator. Or is MD tax rate also applied on my other income made in the state where I live?