The article says the UN has revised its population growth projections to 10 billion in 2050, due to increased longevity outweighing reduced birthrates. That's close to more than 3 billion extra compared to today.
Here's a bit more detail:
At the country level, much of the overall increase between now and 2050A bit of a worry...
is projected to occur either in high-fertility countries, mainly in
Africa, or in countries with large populations. During 2015-2050, half
of the world’s population growth is expected to be concentrated in nine
countries: India, Nigeria, Pakistan, Democratic Republic of the Congo,
Ethiopia, United Republic of Tanzania, United States of America,
Indonesia and Uganda, listed according to the size of their contribution
to the total growth.