I love that you did the math

Fact remains, despite how slim the chances, even without ANY other variation the potential for the 1000 novices to be weak exists. Those odds begin to change when you add in variants like genetic culling of the ability that may have occurred in the region and who knows what other factors. It could be as simple as the region recently underwent the terror of a rampaging False Dragon in Logain and women who would not normally think to become AS suddenly had an opportunity in front of them and went to investigate.

I disagree with DomA on a few points such as AS not awakening the ability in those too weak to become AS. From what we know on the male side, the test itself awakens the ability. In which case the AS would be stuck with even the weak women for several months at the very least. This also seems likely when we look at the Sul'dam, these are women who are on the brink of Channeling but have not yet done so and thus AS cannot feel the ability in them. For all we know there could have been 10,000 women who came to sign up, but only 1000 had any ability at all.

Further, if you look to the Black Tower as an example of voluntary recruits, we've seen some men who went there already had a good feeling that the ability was in them, like Grady and Almaragin (the Tairen lord) who each had male relatives who had could Channel and have proven to be rather Strong. Then look at Androl, who went out of simple curiosity, and he turns out to be very weak. It's possible many women in the 1000 Novices were driven to sign up because very recently they were in the path of Logain and they wanted both a sense of security and a sense of purpose but didn't "feel" the Power in themselves and like Androl they had a small level of ability. Others, like Sharina, had no real reason for leaving established lives (with huge conflicts in fact) and may well have "felt" the Power in themselves and took the opportunity to join. Sort of like having a "Calling" v. a "Vocation"

In the end there are many reasons Egwene could have picked up so many too weak women, but if we were to look at a formalized recruitment that gathered EVERY woman (spark or no-spark) who could channel from EVERY region of the world the 62.5% would be true. I believe that's meant to illustrate both AS ineffectiveness as well as light a path for the future of the WoT world post-TG and perhaps show us what things were like in the AoL. Millions of Channelers with varied abilities who could accomplish more together than they could separately.

Egwene has shown us flashes of what she intends with this throughout the series. She clearly wants to unify the Channeling groups and open up recruitment policies even further.