Is this a contradiction or am I reading it wrong? Genesis 5:28

[Anomalocaris]

He said all the days were 777 years.   Maybe those years just had more days.

Just a then current fashion. "All his days were numbered 777 years." i.e. his days totaled up to 777 years.

And remember, most people would glaze right over when being hit with any kind of higher math* in those days.

*Higher than 5 + 3 = something.

Apparently even in these days the eyes of people such as Neo still glaze over when confronted by pretenses by the Bible at doing math not much higher than 5+3.