Axis V is the global assessment of functioning. It is assessed on a scale of 0-100 in terms of symptom severity and the higher the number the better one functions. People are rarely, if ever, given a rating of 100. 70-90 indicates very mild symptom severity that results in minor impairment. I'm not sure why your social security papers say 50 while the axis V in the psychiatric report says 60, perhaps they were taken from different times or from different doctors? A rating of 50-60 generally indicates moderate to serious symptom severity, however, not to a point where hospitalization is required. Below are 2 links to see the entire GAF:

http://www.gpscbc.ca/system/files/MH_GAF_summary.pdf (PDF form)
http://en.wikipedia.org/wiki/Global_...of_Functioning (HTML form)