That’s just a normal shortcut for mental math. Break your problem into simpler problems then combine, in this case if one wants to know 7+6 this is being turned from 7+7=14, an easy problem to remember, into (7-1)+7=14-1=13.
That doesn’t feel exactly right as it’s not exactly the way you think about it, but words can’t describe such inferences of thought other than to call them what they are which is not exactly how one’s thoughts reflect them.
It seems like game studios cannot possibly do right in this regard. They can either be like valve or rockstar where they are criticized for taking their time, although they almost always put out great original titles or they can be like cd project red where they push out the game as fast as they can and they are criticized for rushing it. There can be no middle ground as to not rush it and to make it a good game may mean delaying repeatedly until it’s in a releasable state, and only the studio can be given that decision.