I read the whole thing in Chinese. It's strange. Never heard of
anything like it before. The black tea undergoes wodui fermentation.
Then the tea is reprocessed using nanotechnology to become selenium
enriched. At the bottom it says some tea growing regions have soils
naturally rich in selenium. That is then abosorbed into the tea. But
only 10% of that selenium ends up in the tea infusion that you drink;
meaning 90% is wasted. So they came up with a way of using
nanotechnology to help the tea growing in the selenium rich area to be
better expressed in the tea. According to the text, selenium has a lot
of benefit to the human body.

Still, it's very strange. Without understanding the process fully, I
wouldn't try it. Doesn't seem natural. If you wanted selenium, since
it's already naturally present in the leaves, why not just grind it
into powder and then infuse the powder in hot water?

Or maybe their "nanotechnology" process is exactly to grind the leaves
into fine particle size, which you then infuse in hot water, meaning
you get full benefit from the selenium in the leaves, since you also
then consume the leaf?