Yes, you must be rooted to use game guardian. I just rooted my phone (Samsung galaxy note 5 sm-n920t 7.0) last night using magisk method, worked good with no issues (you can find it on goggle or xda developers website). Anything for a hack like this it duplicating items requires root so far as I know.
Lol thanks. It's my first time using something like gg and it's not easy to figure out blind lolgoodluck with your findings now,
i can easily guess your condition but all of it worth once you're able to change bunker time,i also used same pause trick with video.
It still works , try to make sure you have to load a screen in between changing the value it seems to work best that way. For me , right before I go up the elevator, I change it to 1 , once I have reactivated the terminal and the elevator has risen all the way, I change it back to the default number 259,200. Rinse and repeat , I reset it a good 15-20 times last night . If you ever mess up, just close the app oit all the way and start the process over. On a side note , I always choose the first address out of the 6 that it always comes up with and so far its always been the right one
actually, it worked perfectly for me too,but last time i reset it like 25 times in a day,so it stopped working
.so I took a break in the game for 12 hours i guess.after that, it works again, but i am facing problem in gas finding a gas tank.thanks though. 
I'll have to check next time I play , I plan on "restarting" the save anyway, so that I can upload it if someone wants , so that it would be more organized I feel.
You don't have to exit the bunker, just wait for the elevator to come all the way up, then change the value back to 259200, after the initial search for the value , you never have to leave the bunker again , unless you mess up the value
