A. Bluffing is a rather cute word for telling lies, and lying is rarely a good idea. Don't bother venturing down that relationship cul-de-sac. Sure, everyone tells the occasional fib, but there is a big difference between pretending you enjoyed your girlfriend's jellied chicken and inventing fictitious sexual partners. One is a well-intentioned distortion of the truth; the other is a blatant lie.
The trouble is, even the whitest of lies is never a one-time-only phenomenon. If she thinks you liked her jellied chicken, you should look forward to eating it again soon. And if you fabricated a whole bunch of past relationships, one lie will lead to another, and sooner or later you'll be found out. Where will your relationship be then?
In any case, I doubt your girlfriend's sexual history requires you to count on fingers and toes.
Theoretically, those numbers should be much closer to each other, but men always report more sexual partners than women. In 2018 Dr Kirstin Mitchell at the University of Glasgow investigated the reasons and concluded that men tend to 'estimate up' and therefore over-report, whereas women tended to 'count down', and so reported more conservatively.
The disparity, it seems, is largely down to male insecurity. Heterosexual men typically get upset about a partner's number of previous sexual relationships because they are afraid that they won't measure up. If your girlfriend had only slept with a couple of men, the competition would be minimal. If, however, she has 15 different notches on her bedpost, statistically your chances of making it to the top of her leaderboard would be significantly smaller.
So women have good reason to play down the number of partners they report. At some point every woman learns that when a new lover casually inquires about past relationships, they don't just want to know the number; they want to know everything. If a woman obliges, then he may start to ruminate, sulk and the arguments come soon after. At which point the woman quite often vows never to share that kind of information truthfully with a partner again.
You'll both be far happier if you can forget about the numbers. Sex is not a competitive sport, and the chances are that your girlfriend is far more interested in your sensitivity, generosity and sensuality than she is in how many women you slept with before her. She probably knows you don't become more sexually experienced by having sex with lots of people. You become more experienced by having lots of sex with someone you feel comfortable making mistakes with.
Besides, if you do feel insecure about how she'll view your lack of experience, lying would almost certainly make her think less of you. To be a clumsy lover after a small number of sexual partners is forgivable, perhaps even endearing. To be so after 50 partners is not.