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@rona11 

1) You're broker is splitting sale-date-1 because the units had 2 different purchase dates, and therefore 2 different purchase prices, and that's the way they report any sale.  But the K-1 is combining them because its using "unified basis" (i.e., average cost) for all units and doesn't care about the differing purchase prices.  So let's say your gain/unit was $10 (from your K-1).  Then on your 1099-B, the 20 unit sale would have a gain of $200 and the 10 unit sale would have a gain of $100.  The IRS will be fine with this, because its correct.  As for the IRS trying to reconcile, at the moment they just get the revenue from the 1099-B (cost not reported, and the K-1 sales schedule not reported).  But even if they received all the same documents you got, and had a question about what you reported (they shouldn't, but who knows what their computer will spit out years from now) you'll have the calculations and rationale to explain it.