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The claim shows one sample that dated to 3.5 /- 0.2 million years before present.
While other answers are correct that the half-life of Potassium-40 is very large, the 0.2 MY error bars indicate that the measurements were accurate enough to establish the "age" with a high degree of certainty.
Unfortunately science is less formal than robotics.
They sent these rocks to 2 labs and had them dated by potassium-argon dating to be between 270, 000 and 1 million years old.
@Oddthinking: Dismissing claims of anomalous data is a No True Scotsman if it is done in a cavalier fashion.
In the philosophy of science, this danger is described by the Durhem-Quine Thesis (en.wikipedia.org/wiki/Duhem–Quine_thesis).
The claim "the real ratio of elements would indicate a 50 year old sample" lies more than 17 standard deviations away from the mean measurement, so it is very unlikely that the sample matched that prediction. The same flow yielded samples that dated to 1.3 /- 0.3 MYA, 0.8 /- 0.2 MYA, and 1.2 /- 0.2 MYA. (One sample also dated to 270,000 years ago, which appears to be the minimum measurable value, so is not a significant aberration).
Radiometric dating would predict that, if the assumptions (1) and (2) hold, samples from the same flow would have the same age.