Pirkei Avos- how does a sieve retain the fine flour?

Question

Regarding the following mishna in Pirkei Avos:

משנה אבות ה׳:ט״ו ארבע מדות ביושבים לפני חכמים: ספוג , ומשפך, משמרת, ונפה.

ספוג, שהוא סופג את הכל. משפך, שמכניס בזו ומוציא בזו. משמרת, שמוציאה את היין וקולטת את השמרים. ונפה, שמוציאה את הקמח וקולטת את הסלת.

Pirkei Avot 5:15
There are four types who sit before the sages: the sponge, the funnel, the strainer, and the sieve. The sponge - because it absorbs everything; the funnel - because it let's in at one end and out the other; the strainer - because it lets the wine out and retains the sediment; the sieve - because it lets out the bran and retains the fine flour.

How does a sieve retain the fine flour and let out the bran? Isn't it the other way around, that sieves have small holes and they let smaller things out, not bigger ones?

Answer 1

Bartenura explains that the desired fine flour is actually coarser than the unwanted dust-like particles which are removed via the sifting process. (The bran is removed prior to this stage.)

Answer 2

סלת is coarser flour; קמח is finer. Source (for example): בבלי מנחות דף עו עמוד ב.