If the player nominates the Brown, strikes it first, and results in both Brown and Yellow being potted - then 2 points are awarded.
SECTION 3. THE GAME
10. Snookered After a Foul
After a foul, if the cue-ball is snookered, the referee shall state FREE BALL
(e) If both the nominated ball and a ball on are potted, only the ball on is scored unless it was a Red, when each ball potted is scored. The free ball is then spotted and the ball on remains off the table.
http://www.worldsnooker.com/about_the_rules.ht m