There have only been so many people alive on this planet. There can only be so many Saints.
Jesus made it very clear that only a few people are going to get into heaven.
With the message from Jesus, it is a statistical improbability that there could possibly be an uncountable number of Saints in heaven, as most people period, are in hell.
This is a number which best estimates the number of people who have ever lived;
prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx
106,456,367,669
Here is another number from a different source, you can see it is fairly close;
math.hawaii.edu/~ramsey/People.html
96,100,000,000
Now, take a look at those two numbers and you will see that both of them are countable and finite.
If every single one of those people are Saints, that makes Jesus a liar, because he himself said only a few will find their way to heaven.
If most are in hell, only a few in heaven, and obviously, even fewer Saints, voila, a very countable number is what you will be presented with.
Like I said, the primitive man who wrote revelation, was a very simple man, indeed.