Thanks so much for helping.
First, I had to set the reviewers group as Repetitive even though none of them are. It then allowed me to select "Number of". HOWEVER, I just noticed that all my People Pickers are now unbound and cannot be bound properly, Yikes!
count(../../my:reviewers) = ""
I tried the following:
BAD count(../../my:reviewers[reviewRequired = 1])
BAD count(../../my:reviewers[my:reviewRequired = 1])
OK BUT RETURNS 1, I SHOULD GET 3 count(../../my:reviewers[//my:reviewRequired = 1])