The arrows on a schedule indicate the first and last game of each day – the system automatically figures this out.  On the Location Details page, you can add your own text as a tooltip for each type of green arrow.  They were built to help indicate who has net duty (ie. first coach puts them up and last coach takes them down.).

The first and last game flag can be enabled by going to Schedules > Locations > Manage Locations > Edit Icon
 
You have to enable it for each location you want it to display for.
 

 
You can even add an optional message that will display on the schedules page.