I’m on my first “Genki 1” lesson but it’s giving me questions from past kanji lessons. How can I get it to only give me questions from that specific textbook?
You may have the "mix weaker items into quizzes" setting turned on. It's some sort of slider in settings -> quizzing, I believe a bit to the bottom. Slide it completely to the left to 'undo' it. Another explanation may be that some kanji in the "Genki 1" schedule are also in a past kanji schedule of yours, meaning you already studied them and you don't have to 'learn' them again, and they may look like random kanji that are not in the schedule