For spaced-repetition, there are two modes: short-term repetition (which we discuss in this article) and long-term repetition, which is discussed here.
Short-term repetition is set within the Quiz Viewer when you select "1m", "5m", etc:
You can reset the default repeat times using the Custom Repeat Time icon in the lower right. By default, we'll use long-term repetition via our algorithm but you can change them using the gear icon, which opens this menu:
Short-Term Spaced Repetition generally occurs during the same quiz. So for example, if you answer items at the beginning of a quiz and say repeat in 5m and you take 10 minutes total to take the quiz, the items at the beginning should be repeated about half way through the quiz. If you stop the quiz at 4 minutes, the items should show up in the next quiz if you start a new quiz within a short time window (should be less than 6 hours). If you miss that time window, they'll be pushed into long-term repetition, and they will be repeated the next day at the earliest.