Escape game 50 rooms 1 - Level 20

I am not

Hi, if you played the Escape room 3 (50 games) level 20, it shows a plane. Inside there is a briefcase that has a code to enter. They show a magazine with 4 numbers and I tried that and it's not that. Then there are 4 holes punched in a carton so I tried those, it didn't work. None of the videos I watched explain how they got the code, one shows a plus sign by adding the magazine number plus the punched holes but that still does not add to the code they enter. No one explained it. They circle it but I tried subtracting the 2 sets of numbers and adding and they don't come up with the code everyone on here shows. I was wondering if you can explain how they got the number for the briefcase as I don't get it...LOL Thanks in advance.