I got the same. I think it means no health problems.
From Medical document http://www.cic.gc.ca/english/resources/manuals/ir/ir03-eng.pdf
S1 = no medical surveillance required
S2.02 = inactive tuberculosis
S2.02U = complex pulmonary tuberculosis inactive / complex non-infectious tuberculosis
S2.04 = Treated Positive Syphilis Serology