in feb 2013 there was an online quiz (of 15 questions, i guess) on this site, in which around 100 (110 or so, if i recall correctly) participated in. The Quiz score gives the score of the members in that quiz, and is visible only to that member (i.e you can't see my score, and i can't see yours etc.) Since you didn't participate in that quiz, there is no value being shown for you.