From what I can see, if you claimed itemized deductions, "Tax expense" on the Tax History Report is the amount of the total deduction for "Taxes You Paid" on Schedule A line 7. If you used the standard deduction, "Tax expense" is the amount of taxes you could have deducted if you had used the itemized deductions. However, if you knew you were not itemizing, you might not have entered all of the taxes that you paid. In that case, the "Tax expense" figure is the amount you could have deducted based on only the taxes that you did enter.
To put it another way, "Tax expense" is the amount from Schedule A line 7, whether or not Schedule A was actually included in your tax return.
