I understand that a nondividend distribution is not considered taxable income until my distribution exceeds my basic in the investment. However, in my situation, I bought 85 LVS on 02/15/2013 (My basic cost was $4482.75) and already sold all 85 shares in 05/22/2013 for $5896.94. During these timeframe, I received $20.53 as nondividend distribution on 4/1/13.
When I file my tax , should the basic cost of 85 shares be calculated as:
Initial basic – nondividend distribution = $4482.75 – $20.53 = 4462.22 ??

I really don't know why in my 1099B - Box 3 it listed $4468.78 was the basic cost. Can you give me some advice?