I believe that if you and your sig other's 'numbers' are close to the same...there is a good chance that you have a decent amount in common. Well...hard to explain. Maybe you are on the same sexual level as well as what your beliefs are with sex.
I have this theory...many women who have had A LOT of sexual partners tend to give something away to every person that they have been with. When they have been with A LOT of men...they have very little of themselves left to give...and can really be cold hearted and live a care free life. I just feel that many women who have a BIG past...can do whatever they want and feel little remorse for what they have done...and maybe the two are slightly connected. It may not have to do with sexual partners...it may just be their personality. Correlation is not the same as causation.
Maybe I've just watched too much HBO and Jerry Springer lately