Looking for help with Dad's NJ pre-adoption birth certificate

Sent away right away for my dad's original birth certificate when records opened in January 2017. We are perplexed by something on it... It says both parents were 30 and that there were at the time 11 children still living that were born to the birthmom. I have tracked down my dad's niece and she says the family is only aware of 2 children of this birthmom -- a male and a female. She's convince the 11 is actually 2 "tick marks" -- one for one boy, one for one girl. Seems odd since there are regular numbers used all over the document. I just had someone point out the 11 asterisks that appear next to the question, "Children born to the mother:" Do you think that solidifies the 11 children? 11 just seems bizarre due to the timing.... birthmom graduated HS in 1932. Had son in 1938 that she kept. Had daughter in 1942 that she kept. Had my dad in 1946 and then gave him up. I would love to see other examples of birth certificates from the time to compare!