You sir, have the wrong understanding of the Adrenaline concept

The documentation is right, it is an integer.

describes how adrenaline works:
Adrenaline is in points. When you strike an enemy, you gain 25 points. You also gain adrenaline when being hit by the enemy yourself, this is only a few points though, not strikes (25 points).
Not all skills follow the (25 * strikes) rule though, so you may have to manually check the adrenaline of a skill, when it is fully charged to know its "max adrenaline".