When setting a Safe Saving Level, Digit will continue to save for you as long as your checking account is above the amount you set.
Setting up Safe Saving Level
1) Tap on your connected checking account in the Digit app
2) Tap Settings to see a menu slide up, and then tap Safe Saving Level
3) You'll then be brought to where you can enter a new Safe Saving Level
You can also login at Digit.co, and change your Safe Saving Level by heading here.