Most scientist agree that Libby was off by 162 years. This process of dating has several problems, as most scientists will admit. Scientists are not sure, and not even in agreement upon how to determine what their findings say. The Scientific Analysis When viewing radiocarbon dating even from a scientific point of view, it cannot be accepted. There are simply too many errors, inaccuracies, assumptions, uncertainties, difficulties, variations, and unknowns.
Science has already repeatedly prove itself wrong here.
The only credibility it can offer is in samples less than 40 years old, because, before 1948, no records were kept. Since science relies so heavily on assumptions, let me offer some. Perhaps the half-life of carbon changed due to irregular atmospheric conditions or due to the great flood. Perhaps thae level of radioactivity of 14-C has changed. But different isotopes yield different dates for the same rocks.