Why do city tax value differ between title screen and county screen

This is more of an educated guess then a completly true answer since i can't test it myself at the moment.

When i add together all the taxes you should get from your first image i get a value of 30.2 gold, however the calculated number in the outer list only shows 18.54. Even further when i add all you tax categories together its also short of 1 gold to the 108.19 you should get.

In my opinion this is most likely a visual bug and the numbers there forget to incorporate some modifiers. Another possibility could be, that the gold amounts shown besides the names of the mayors is the full "normal" amount you would get and depending on the color (red, yellow, green, etc.) this amount is in reality either reduced or increased because of modifiers not stated there.