I happen to have a copy of this years blueberry pollination contract from
the Jasper Wyman company (of Maine, and now in PEI as well).  I believe they
rent well over 10,000 hives in Maine.  Blueberries flower slightly earlier
than apples (only a few days or a week).

From that:
"The minimum standard is 6 frames of brood and 8 frames of bees.  If the
inspection team determines, in their opinion, that a 4 or 5 frame hive has
more than enough bees to provide adequate pollination, they will mark that
hive as a 6 frame hive.

Payment will be based on the inspection as follows:
0-3 frames of brood                           $0
4-5 frames of brood                           20% less than base rate
4-5 frames of brood with a solid box of bees= base rate
6-7 frames of brood                         = base rate
8-10frames of brood                           20% more than base rate

The base rate for crop pollination year 2000 will be $50.00"

End of quote.   That is US$

My understanding is that a frame of brood is any frame with over 50% coverage.
However, the contract does not spell this out.

3% of the hives are tested.  You cannot "fool the grower" as it is a
beekeeper doing the testing.

Regards, Stan