It’s weird because Switzerland is one of the most armed countries in Europe, as in they have firearms but barely any shootings of any kind (so you don’t often hear news equivalent to a guy shooting students in a classroom or killing people at a shopping mall over there). Part of it has to do with the draft (most people who purchase firearms have a form of training, as they learnt how to properly handle them during military service).
120.5/100 == 1.205, it’s the exact same number expressed differently. However, 1.205 implies that everyone has at least one firearm, which is not true. 120.5/100 implies that if you go to 100 random people and count all their guns together, you’ll end up around 120 guns on average.