My apologies... I'm actually hoping to update Sheet 1 (the line graph over time). I realize now that my original post does not have the right numbers, as you'll see below. What I'm trying to do is calculate the total number of distinct locations ordering to date (for that week).
For week 1, we see 19 distinct locations ordering.
For week 2, we see 56 distinct locations ordering (this includes the 4 locations re-ordering.)
For week 3, we see 78 distinct locations ordering (this includes the 5 locations re-ordering)
I believe the reason is because for those locations that are re-ordering, they get counted as 2 (and higher for more recent weeks), which I'm guessing is why the count gets messed up when trying to do a running total.