Calculating FREE to PAID conversion RATE is a bit ambiguous...

I am calculating the rate for free-to-paid conversion rate.  There is some ambiguity in the your definition of Conversion RATE:

"This metric measures the proportion of engaged students who choose to benefit from full course access on the 365 platform by purchasing a subscription after watching a lecture.

It is calculated as the ratio between:

    *The number of students who watched a lecture and purchased a subscription.
    *The total number of students who have watched a lecture."

The bold "after watching a lecture" and the "who watched a lecture and purchased a subscription" are in contradiction with each other.   There are many students who purchased the subscription *and* watched a video on the same day, and then there are many who first purchased a subscription and many days later watched the video.  So the first bulleted item is incorrect IF we want to only see if watching videos converted a student into buying a subscription.  So, I am going to continue to solve this in a way that only those that purchased after watching a video will be counted in the *FREE*-to Paid conversion rate.  

It is very important to be precise in the questions you are presenting us with because we waste a lot of time waiting for an answer to question here because we don't have a colleague to ping in real time, to ask them questions and make sure that we are on the same page when making these calculations.