Here is the whole quote:
First, reliable change and recovery were assessed using the male adolescents’ report of symptoms
on the YSR. Of the 155 males who completed the YSR at admission and discharge, 81% of
adolescent males reported some amount or degree of symptom reduction. Of that, 31% reported
improvement that exceeded the 2 standard deviation cut-off for reliable change (>28 raw score
points) and 50% reported improvement below the cut-off for reliable change (<28 raw score
points).
so what this means is 81% of the kids reported some degree of symptom reduction... of these 81% , 31% reported improvement that exceeded the 2 standard deviation... 2 standard deviations is 95.5%... so 31% of the kids did extremely well and exceeded expectations. 50% reported improvement below the 2 standard deviation mark (which is below 95.5%).
50% + 31% = 81%
So 81% of the kids reported a reduction in symptoms and of these 31% did extremely well, 50% did as was expected.
...