Alerts and field selection

Quite new to alerts but have noticed I can’t select the Summary chart to trigger an alert if I have more than one value column.

Could a drop down be added in the setup to be able to select which column you want to be used in the alert?

Currently I’ve had to create my report twice, once with all the columns I want to see, and the other for only field I want showing in the Alert.

If I’m missing something please let me know.