If the amount you calculated is less by a small amount, I would be inclined to use the amount in box 1b. Thus A1=A2 and B1=B2 and finish up. Otherwise the percentage is wrong or some other error. Then you would have to contact Vanguard and explain all this to a service rep and have them send you a corrected 1099-DIV or the correct percentage. That could result in a long delay.
