Who are these two brokers?
As a "fully taxable" merger that means gains and losses are allowed. Box 7 checked would indicate that this was a more "typical" cash plus stock transaction where gains are allowed, to the lesser of "economic" gain or cash received, but losses are not, all calculated on a lot by lot basis.
Guidance provided by Takeda per costbasis.com: https://www.costbasistools.com/taxstmts/ShireTakeda.pdf
