After entering in the desired adjustment from the LABOR tab in Line Items view, the new total should calculate based on the number of occurrences for each month.
TIP: The fractional (decimal) value of the dollars will not be displayed in the User Interface, however they will be used in the calculation
For example:

Typically, you wouldn’t worry about the pennies but some people enjoy perfection. In this example, an 8% increase has been added to the base annual wage of $130,400.00 in the LABOR tab.
If we examine the totals in OPEX, we see $10,867 for 7 months and $11,736 for a total of 5 months. Add these months up and you will get a total of $134,749. Where did your two dollars go?
This is what it happening:
$130,400.00 ÷ 12 months | = | $10866.666666666670 |
$10866.66666666667 X 8% | = | $ 869.333333333336 |
$10866.666666666670 + $869.333333333336 | = | $11736.000000000010 |
$10866.666666666670 | X 7 months = | $76066.66666666669 | | $76066.66666666669 |
$11736.000000000010 | X 5 months = | $58680.00000000005 | + | $58680.00000000005 |
The decimal values are rounded up | è | $134746.6666666667 |