Prior to 1978 one credit was earned for each quarter in which you had at least $50 covered earnings. Our software only knows about annual earnings, not quarterly earnings. From 1978 on it doesn't matter how the earnings are distributed throughout the year.
So, our software potentially calculates too many credits by giving four credits for annual earnings over $200 prior to 1978. If all of the earnings were earned in a single quarter, then you'd actually earn only one credit. This can particularly occur when people had summer jobs during school years.
Short of requiring input that is not readily available even from the Social Security website, i.e. earnings by quarter for every year before 1978, this is the best we can do.
If our software finds you to be qualified for Social Security when Social Security says you don't have enough credits, just delete your past earnings.