There are almost always several ways to read or pronounce one kanji and they can be separated into two categories which are 音読み(on yo mi) and 訓読み(kun yo mi). I found some nice explanation about those online; here is the quote. "Most of kanji have two different readings of On-yomi and Kun-yomi, which are reflected of sound and meaning. Onyomi is originally from Chinese pronunciation, and Kun-yomi is the translation into Japanese native word." So in this case tami is its 訓読み and min is 音読み. 音読み is often used in Japanese idioms such as 国民 (kokumin). Hope this helps!