I'm being charged a $297.85 Tax offset from 2013 after using Turbo Tax to file my returns. This seems like a high number. on top of the $776 I paid in taxes that year.

$1073.85 in taxes paid on $18,000 seems high and is above my tax bracket. Why am I being charged an offset? Why didn't Turbotax provide me with an accurate number for my tax payments?