I was thinking about it when I first read that particular session. As a result was I decided the number whether 19 or 119 million did not really matter and there was nothing mystical about it either.
It does not mean the "best" people out of 6 billion survived. Or the most spiritual, or most technically and survival adapted or physically and mentally strong.
Let`s take our world`s history as a guide, and we will see there has not been a century without a major conflict.
Heck this 21st century (not even quarter way in) we got Afghanistan and now Ukraine amongst other smaller conflict or open war. Last century there are 2 world wars plus Korea, Vietnam and Iraq. A century before you got Napoleon, and another before then you got 100 year war in Europe. We are quite literally in a permanent warfare since the time of the last cataclysm.
So back to our 19 or 119 million survivors. It could mean that not all other people died right at the event of cataclysm, but somehow made it out alive, were struggling beyond their capabilities and died shortly afterwards. When everything is scarce and what is to be had can only be taken from other living people...
It the same session or one after it was also mentioned that those alive may be envious of the dead. They would be seeing red dawns, parched grounds and very little hope to go on.