hashing – what are those in ch. 8 of "An Introduction to Algorithm Analysis" by Sedgewick

In chapter eight of "An Introduction to the Analysis of Algorithms" by Sedgewick (1996 edition) the problem of the coupon collector on page 425 is presented.

My confusion is how can I identify the k collections. A k collection is defined as:
"a word consisting of k different letters, where the last letter of the word is the only time the letter occurs"

In Exercise 8.6 of the book, all 2 collections and 3 collections are found in Table 8.1. There the configurations of 4 balls are displayed in 3 urns

If I try, I would say a 3-collection from Table 8.1 is 2213, with the last letter (number 3) just ending, but I'm pretty sure I'm wrong.

Can anyone help provide an example of a k collection (2 or 3 collection) from Table 8.1? Many Thanks