On the First of the Sabbaths, or SUNDAY.
When the Jews reckoned the days of the week they always used the day in it's relationship to the Sabbath.
Sunday was the first of the Sabbaths.
Monday was the second of the Sabbaths.
ect.
For example, one of the Pharisees said he “fasted twice in the Sabbaths”, a reference to their twice in a week fast.
And on the road to Emus, one of the men traveling with a disguised JESUS said, concerning the events of the past days, “Today is the third day”.
I may have missed something in your explanation of the Jews counting days of the week in relationship to the Sabbath. So, I still fail to see how if Jesus rose on Sunday morning, one can count back three days, three nights and arrive at a Friday afternoon death?