State tax filing

Please let me know if I understand correctly.  Example:  Michigan resident working in Toledo pays $2000 on W-4 to the City of Toledo.  Amount of MI taxes owed is $3600.   I write $2000 in Box 18a and subtract that from Line 17  ($3600 - $2000 = $1600)  So the amount of taxes I owe Michigan is $1600?  And I write that in Box 20?   

 

Thank you so very much for helping me wrap my head around this.  Using actual numbers to plug in the equation somehow helps my poor, over-wrought brain to understand.  Your time and expertise are much appreciated.