Nothing to explain. NVAX needs $7 million for one last flu phase II (they have done a bunch of very successful phase II's already), and $90 million for one flu phase III.
So, BARDA gave them $97 million for the next 3 years. And, just in case they needed some extra money later on, they might give them more later on, for a total of $179.1 million. This extra money for years 4 and 5 are definitely in case extra work needed to be done for a possible new pandemic strain that may emerge by then.
NVAX flu vaccine is now 100% guaranteed to be marketed within the next 3 years, and possibly before in the case of a pandemic strain.