premise: The traditionally teen-friendly app now counts 14% of smartphone users who are 35 or older as users, as compared to 67.5% of users ages 18 to 24. It remains to be seen whether the arrival of older users will be a turnoff for Snapchat’s core audience.
hypothesis: There are more users who are above the age of 24 then there are who are under it.
reason: This is definitely incorrect, since 67.5% of users, according to the context, are aged 18 to 24.  Therefore it is definitely incorrect to say "There are more users who are above the age of 24 then there are who are under it."