Kiwi - Your math is correct, if scripts continued to increase at the rate observed this week, they would double in 20 weeks because 1.0357 raised to the 20th power is 2.01.
I am optimistic about script growth, but to be realistic, it bounces around from week to week and we just had one of the better weeks. About half the increases will be below average. But, on the other hand, growth does clearly seem to be not just increasing, but accelerating, which makes sense as 1A effects continue to take hold, so doubling in 5 months or so does not seem out of the question to me, even without considering the interim look.