I’m confused on how to report non-statutory stock options on the 1040.

My client exercised his option to buy company stock and then sold the stock the same day. His W-2 shows Code V in box 12 for $10,712.64. I have no problem with the W-2. But I also have a 1099-B from the brokerage firm who handled the sale and the sale price ($18,922.77) minus cost basis ($10,229.70) shows gain of $8693.07. I assume I must include the 1099B info on Schedule D but it seems like this is reporting the gain twice? What am I missing?