Possible solution: 
	 
	Add a getter in your CustomBreakManager to calculate time left as you did in shouldActivate()
 
public long getTimeLeft(){
	//Logic here
}
	 
	In your main script extract the breakmanager variable:
 
CustomBreakManager breaker;
@Override
public void onStart() {
startTime = System.currentTimeMillis();
getExperienceTracker().start(Skill.MINING);
// Initialize the customBreakManager instance
breaker = new CustomBreakManager();
breaker.exchangeContext(getBot());
bot.getRandomExecutor().overrideOSBotRandom(breaker);
}
	 
	Add in your paint:
 
if(breaker != null){
long timeLeft = breaker.getTimeLeft();
//print it out
}
	 
	EDIT: 
	I see you already did something similar, but I believe you are using the wrong breakmanager variable? 
	Where does the customBreakManager variable comes from so suddenly? 
	 
	This line -> long timeUntilBreak = customBreakManager.getNextBreakTime() - System.currentTimeMillis();