Thank you for response, Roger! It makes everything much clearer.
As for wisdom, that’s not me, but JW Player 
However, I see that BWCheck uses the whole traffic per period to calculate bandwidth. So, together with my solution (without multiplication) it actually needs 1 packet to be sent to calculate the bandwidth(if second, for example, elapsed).
I understood your thoughts, but you actually didn’t say if it is better for player-in-browser users to migrate to my modification or to leave with initial BWCheck.
By the way, I was a bit confused that nobody in this thread was not confused with speed like “20000 kbit/sec” (I’m sure they’ve got it).
m…