You are referring to Exception 1 in the instructions. Here's what it says.
your shortcut is basically pretending 100% of the transactions have no adjustments
You are also reporting the information on the wrong line.
Exception 1. Form 8949 isn't required
for certain transactions. You may be able
to aggregate those transactions and report
them directly on either line 1a (for
short-term transactions) or line 8a (for
long-term transactions) of Schedule D.
This option applies only to transactions
(other than sales of collectibles) for which:
You received a Form 1099-B (or
substitute statement) that shows basis
was reported to the IRS and doesn't show
any adjustments in box 1g, and
You don't need to make any
adjustments to the basis or type of gain or
loss (short term or long term) reported on
Form 1099-B (or substitute statement), or
to your gain or loss.
