Well adjusting the basis is easy enough. When you enter the sale using the default 1099-B entry form enter the 1099-B as it reads but then click on the "I'll enter additional info on my own " blue button. On the next page enter the correct basis in the "Corrected cost basis" box. TurboTax will report the sale on Form 8949 "as reported by the broker" but will put an adjustment figure into column (g) of the Form, a code "B" into column (f) of the Form, and the correct amount of gain or loss which includes the adjustment.
However, brokers are the experts when it comes to reporting basis so I'd first ask the broker why the basis being reported isn't the $30,884 you'd expect.
