Title is total link bait. Article says 3.5% of Android phones clocks are off by 15s and that in some cases there are time zone edge cases causing it to be off by an hour. This is not what the title conveys.
Actually 3.5% of android clocks ARE out by one hour or more... the 15s bug effects some phones, but the problem of being more than an hour out is very general and does effect 3.5% of phones - sorry if that's not clear!
They explain the math pretty clearly under the heading "How Widespread is This?"