It’s not completely different — it works under the same principle as all timing charts. It just has a slightly different layout.
As you can see, there are three columns showing the cam number and then the contacts. The leftmost column is the cam, the next is the first contact, and the one after that is the second contact.
You’ll notice that you have two “options” for what the second contact will be in that third column. That just depends on what position the cam is in, and you can tell that by looking at the rest of the timing chart.
As I said in my previous post, please take the time to review the first video in module 5, unit 5 of Fundamentals. It covers this exact timer chart and shows how to read it.