Customizing MyMetrics to show you the metrics that matter to you the most can be done in the application preferences. Once there, select the appropriate category of metrics and enable/disable the toggle next to the metric. When a metric is enabled, a goal can also be set, which will customize the chart display, showing you the workouts in which you met the goal.

Building this version of MyMetrics took 2 months of my spare time, which is why select settings require the Premium purchase. The free version lets you customize your performance metrics, but once you’ve decided that you like the app, you’ll likely want to unlock Premium with a monthly price of $0.99 (price may vary from country to country).

MyMetrics counts the number of classes in which it has workout data. I'm not sure when they started providing the metrics via the official app, but if you can find a workout there, it should show up and be counted in MyMetrics.