That's pretty straightforward. There are 128 million people working full-time jobs in the US. The full-time median income in the US is between $48,000 and $52,000 for 2019 depending on your source. The BLS says it's about $48k for the third quarter of 2019.
The often quoted lower median figure, in the $30,000s ($34,000x for 2019; it was ~$33,700 for 2018), is the median income for all US workers, including people working relatively few hours.
Being conservative, the US has at least 60x million people making $50,000 or more per year. That's ignoring anything that doesn't show up in the BLS numbers.
Now consider how massive the rest of the global economy is and the tens of millions of people in dozens of other countries with high incomes. The US all by itself eliminates the possibility of $34,000 being the 1% line.
With the strict US median at the $34,000 line, that's ~78 million workers at or above that level. Again, that's for one country.
China has a very large number of people earning around the US median now, due to their scale. They add tens of millions of more people to the over $34k group. Then include Western Europe, they add tens of millions more. And so on.
Just FYI, to be in the global one percent you need an income of $32,400 per year