Take the low risk approach and consider your online record is erroneous. If the CBP Officer, upon your arrival, marked 3 months long stay on your passport, that is it. Do not try to benefit from discrepancies like you mentioned, if you want your subsequent visits to the US be smooth and frictionless.I am going to go out on a limb here and say, if you came to the US for an even which will end at a certain time, much before the said 3 months, I suggest leaving shortly after your purpose of visit is complete. For instance if you told the CBP Officer that you are here for a 2 weeks long conference and want to visit an old friend before you go back home, I’d suggest not extending your visit beyond a month. 2 weeks for the conference and 2 weeks for social visit. And you are done. If you stay longer, it means, you have no reason to go back home (your job is not important to you, your family you couldn’t care any less, etc.), portraits you as the perfect example of a potential/future illegal alien, causing cancellation if your US B1/B2 visa.