If I recall correctly, because sometimes extraneous, and erroneous information gets lumped in with the correct information in these database files.
She is not saying that he hasn’t used up to 16 different numbers but she can’t prove it so she is only focusing on what she knows is true.
The number Obama used on his tax forms came from Connecticut at a time when Obama would have been only 15 years old and living in Hawaii (supposedly).
Once it is proven that he is using one SSN# the dominoes will fall regarding the other fake SSN#s.