The phrase "few billions" means a small number of billions. It implies that there are only a few billions, rather than a large amount.
Sentences with «few billions»
At some point in the last few billion years, dark energy became dominant in the universe and thus prevented more galaxies and clusters of galaxies from forming. (britannica.com)
All of these plans need to be altered if the population is going to grow an extra few billion. (sciencemag.org)
Their remarkable result: The universe had been slowing down for its first few billion years, but then it started speeding up. (discovermagazine.com)