It's 2 pts for every $10 of spend, so in the case above:
$63.26 / 10 = 6.326 * 2 = 12.652
If you were awarded 13 points, then you have your answer.
How about when I was awarded 12 points instead of 13?
That is the reason I'm asking this. I do know $63.26 / 10 = 6.326 * 2 = 12.652