It's probably due to rounding errors.
If you open the 1099-B works in the forms mode errors may show up with a red ! and highlighted. This may give you an indication of what transitions need to be adjusted.
To switch to Forms Mode, open your return and click the Forms icon in the upper-right corner of your screen (or choose Forms from the View menu at top).
The 1040 Worksheet will display and all the forms in your return will be listed on the left side. Simply select a form to open it.
To switch back to the interview, click the Step-by-Step icon in the upper right corner, or choose it from the View menu.
