Abigail birth says about 1629, this means to me that this could mean a plus or minus a few years, if George was born in 1640, as we don't have a month this could be late in the year, that his mothers birth date is about 1629, take a couple years less and it is possible, Henry VII, mother was only about 13 and 1/2 when she gave birth to Henry. So I don't believe these dates are a problem.
The problem is that the date of the marriage of the parents of George is 1648, while George is born 1640, if the date of the marriage is correct and George is their son then the date of the birth of George must be wrong. (I am assuming here that he was not born out of wedlock)