The reason is because the results you get, ‘superior’ ‘high average’ etc are only RANGES that contain your actual score. Your three superiors could have been borderline ‘high average’, while your friend’s two may be on the higher end of the superior range.
Your friend may have still gotten a higher total score than you, despite the results you’re told which seemingly suggest otherwise.
But please keep in mind, the select entry test doesn’t mean that much in the long run and doesn’t limit your performance in VCE at all. If you are truly a gifted student, then you would do well in VCE regardless of your cohort.
Btw if it offers any comfort, back when I did the test I got four superiors and still got rejected from Macrob, Nossal, AND Cory. Seemed like the end of the world back then, but now I couldn’t care less.