MandarinBanana uses a mnemonic system where each Pinyin is split up into two parts: an initial and a final. This is different from other systems for splitting up Pinyin into initials and finals, so you'll find different initials and finals in your 标准教程 Standard Course HSK 1 textbook. The creator of this specific method, Serge Gorodish, named it the "Marilyn Method". Sometimes I refer to the initials and finals of pinyin syllables as "Marilyns".

Let's not dig into the entire system here - instead, let's stick with our goal: to learn the character 你. In this system, the initial is "ni", and the final is "Ø3", which means "take the initial 'ni' and don't add anything to it, except for the third tone". On the next lesson we'll have a look at "ni" first before getting to "Ø3".