Each day on the Calendar will display a summary of your activities on that day, with various features available to view a snapshot of your training on this day. The summary items for your activity can be customized to your chosen metrics based on which items you find to be the most important. To customize your day fields, click the menu in the upper right corner of the workout sidebar, then select Customize day fields

From the customization tool, you can add, remove, and re-arrange items. You can also opt for different items depending on sport by clicking different options from the drop down in the upper left. 

Note: Items not present in your activity file will not show up on the day summary, so it's OK to select items that are not present in all activity files.