I am overriding the Out of the box AEM scheduler and name of the scheduler is ExpiryNotificationJobImpl.
 
Details of OOTB scheduler ExpiryNotificationJobImpl has been given below -
1. package : com.day.cq.dam.core.impl
2. bundle : com.day.cq.dam-dam-core
3. No service rank was defined here
 
I have overridden ExpiryNotificationJobImpl scheduler with higher service rank as you could see below -
 

After overriding and deployment , I am using similar cron expression to check which one will be triggered. But noticed both are getting triggered simultaneously.
 
I have added one message in overriding scheduler to identify my overriding scheduler easily. Even log file is showing both are getting triggered.
 
My plan is to trigger only overriding scheduler not OOTB one.
 
Please suggest.