Building a Ferris Wheel step 9

The instructions say to, " Create a selector to target your second .line element. Set the transform property to rotate(60deg) ." I know the answer (because i got it wrong and the Hint told me) is, .line:nth-of-type(2). Is that something that should be common knowledge? Have I been asleep this entire time? How is that the answer, and how was it determined? Im suddenly feeling like i’ve missed out on something. Thanks in advance.