You are correct with them being six, but they did "rule out" about half of the original number.
"But we have one hundered and fifty test subjects to consider, and the facilities and funding for only half that number. It's simple mathematical elimintation, Lieutenant. That child was one of the lucky ones--either that or he is extraordinarily fast. Either way, he's in." -Dr. Halsey FoR
But half of those 75 kids DID die when they were augmented.