In 30:4, Surah Al-Rum Ayah 4, why does بضع is translated to "three to nine"

In 30:4 , Surah Al-Rum Ayah 4, the word بضع is translated to "three to nine" in Saheeh International. > Within **three to nine** years. To Allah belongs the command [i.e., > decree] before and after. And that day the believers will rejoice The word seems to mean "a few". I want to know the basis of translating it to "three to nine", with primary sources.