The rate of loss of helium from the atmosphere into space is calculable and small.
Now, the only real source of helium in the world comes from underground deposits where a geologic feature (saltdome/petrol?)managed to trap the helium, preventing its escape into the atmophere and on out of the gravity well.
If such decay took place for billions of years, as alleged by evolutionists, much helium should have found its way into the earth's atmosphere.
You seem to not want to read the actual study as well, I am only giving bullets. If you want to see how the numbers work out read the damn study. Gentry, R. V. et al, "Differential Helium Retention in Zircons: implications for nuclear waste management," Geophys. Res. Lett. 9 (Oct. 1982) 1129-1130.