The Auto lock is to emulate a lock style feature. When you arm the keypad it “locks” and when you disarm it “unlocks”. Many folks use the keypad to control a secondary device like a garage door or patio relay etc. When auto lock is enabled it will automatically relock after being unlocked after the configured time. The auto lock controls will show up in the new app once ST adds support for custom controls to the new app.
The countdown is a feature of the keypad where it announces the time remaining for arming or disarming the keypad. This is controlled through a supporting SmartApp when a delayed arming or disarming is setup in the app: [RELEASE] Security System: Intruder Alert with Actions