Type numbers directly into the cards to change all 12 values. Compare the mean (sum divided by count), median (the middle value when sorted by size), and mode (the value that appears most often) with dashed markers.
Why do we need three different representative values? Because which one best represents the real picture depends on the situation.
The most commonly used one, the mean, has the advantage of accounting for every value, but it can swing a lot from a single extremely large or small value (an outlier). For example, if a company has 9 employees earning 3 million won a month and the owner alone earns 30 million, the "average salary" comes out far higher than what most employees actually make. In cases like this, the median is a much more realistic representative value — since it only looks at the value in the middle of the order, it's not easily swayed by extreme values.
The mode plays a somewhat different role. Since it's "the value that appears most," it's more useful for categories (like the best-selling shoe size) than for numbers in general. But if every value is different, there may be no mode at all.
Try picking just one card and changing it to a huge number. You'll see for yourself that the mean jumps way up while the median barely moves.