In this Chinese lesson, students revised numbers from 1 to 19 and focused on constructing larger numbers starting from 20. The instructor explained how to differentiate numbers such as 12 (十 二, shí èr) and 20 (二十, èr shí), highlighting the structure for combining numbers, where 21 is expressed as 20 (二十, èr shí) plus 1 (一, yī), yielding 二十一 (èr shí yī). Additional examples included numbers such as 23 (二十三, èr shí sān) and 29 (二十九, èr shí jiǔ) before transitioning towards 30.