>>537691278
Each weapon has a certain range where it gets a damage bonus applied to it if the piece of the boss if you're aiming at is in that range. SMG = close up, AR = mid range, SR = far range. You can tell if you're getting the bonus on a certain character because the targeting reticle changes color (I think blue?). This dynamically changes throughout a fight as the boss moves closer or farther from you.
Note that I said "piece" rather than "boss", because it seems this is based on the boss's 3D model, not just 1 fixed location its considered to be in. For example, consider Indivilia who has a tail coming out of the back of her. If you aim at her head, which is in front and closer to you, it may be considered mid range, but if you aim at the tail, which is farther back, it may count as far range. This is just an example; I don't think she works like this but for some bosses where you aim does matter on whether or not you get the bonus.
So going back to the kit, since snipers are far range, they're only restricted by the minimum value. That is, the target must be a certain distance away from them to get the bonus. The buff makes that certain distance smaller, or in other words the boss can be closer to you but you still get the range bonus when you otherwise wouldn't have without the buff.
