Students begin by working on Learn Them and progress to Tables Workout. Once a student can do the Tables Workout in less than say 2 minutes they are ready to start testing out how many they can manage in 1 minute. So they try a 1 minute Tables Challenge. Any student who can score about 15 is probably ready for doing Tables Challenge.

Learn Them is for help to learn them.
Workouts is a practice tool.
Tables Challenge is a testing, evaluative tool (not a teaching tool).

Help your students get familiar with their tables by doing Fact Families, listed under Tables. Number Bonds is the addition facts counterpart.