This means you can increase your Endurance by 5 points, instead of just one. If you increase the Armorer skill by 10 points in one level, you'll get a x5 modifier for Endurance when you level up. For example, the Armorer skill is linked to the Endurance attribute.
Each skill has an attribute associated with it. To really power level, you need to get the maximum modifier possible for each attribute. Some skills are easier than others to increase, we'll go over the method for all of them. Trainers work well if you can find them, but you'll need money. But what if you want to increase certain skills quickly? There are three ways of doing this: trainers, books and using the skills. In the natural course of the game you'll increase your skills and gain levels. In-Progress: This guide is still in progress, I'll add information for new skills as I finish writing them.