Kevod HaRav, If Hashem promised Avraham avinu that his offspring will be plenty like stars and sand, why are we such a small percentage of the world?
That is an excellent question. Actually the Torah itself seems to answer that question of how much is ‘like the stars’ since at דברים א,י Moshe Rabenu says ‘Hashem made you many, and now you are as much as the stars’ although they were 60,000 people (men), we see that the Torah itself points to the number of stars as 60k although there are much more, and therefore you must explain that when Hashem gave that Bracha it wasn’t to be explained literally and precisely, but He meant a large amount.
Rashi explains it a bit different and he says according to drash, that the nation of Israel are like the stars that are existing forever.
הנכם משולים כיום, קיימים לעולם כחמה וכלבנה וככוכבים.
When dealing with the sand the navi says יהודה וישראל רבים כחול אשר על הים לרוב.
Which also must be defined the same way. Either using such examples to demonstrate a large amount although it’s not precise or to use that as a parable as mentioned above.