7 trillion looks like a typo, but no, the maths shows that either by continuing the actual global population growth levels typical the 20th century, or achieving 2% per year or far less than what is currently happening in Nigeria, the maths produce this number in a relatively short time!
A key theme of this blog is that, while population growth is no longer the threat that it once was, economic policy has yet to adapt to the slowing in population growth. While population growth has slowed since the 20th century, growth is not at 2% as some dangerous people advocate, and all the world is not like Nigeria, it is still worth understanding just how quickly things can escalate and not take for granted the slowing population growth that is both happening, and needed, to avert crisis.
Does it feel crowded now? Can you imagine Earth inhabited by not 7 billion (7,000,000,000) humans, as we have now, but 7 trillion (7,000,000,000). That would be one human for every 3.3 meters x 3 meters of habitable land on the planet (calculation below). Around 10 square meters allocation per person to live, grow food all of one food and that is without allocating any wilderness for other living things or trying to allow space (corridors?) to move outside your own space. This is a level we would reach if were able to continue peak 20th century population growth rates.