Two thoughts...many possibilities, but to me, not that big of a deal because in both briefs, there is the word "improvement"
1) As shoeman I believe pointed out, the original brief discussed the cognitive 2a part B results at week 12, but because this would be an interim report, it is more appropriate to discuss (in the limited word count of a brief) the completed trial which is 2a part a (and hence 5 weeks)
2) Why are both versions still posted? For some reason the conference couldn't / wouldn't change the final program with all of the other briefs included. Because the conference began today, they all went to print, etc, so they probably felt compelled to keep the same one online as they distributed to the attendees in hard copy.