I did that, it was fun.viewtopic.php?f=2&t=9055&p=89561&hilit=my+life#p89561
What you are measuring is the maximum effort you put out on your top set for a particular day. That is the one number for the day. You do not measure how many sets you did, that does not matter, just the top set that you did with the most weight.
Since on any particular day you might do 5 reps, then 3 reps another day, you resolve these to an effective 1 Rep Max with this formula:
Effective 1 Rep Max Weight = Weight + ( (Weight * .0333) * Reps )