Xbox One Guardian Halberd Glitched

I have a Guardian Halberd on Xbox One that says it does 3-10 random damage. I have used it at least 30 times and have never done more than 7 points of damage with it, and that only twice! (never done 6 as far as I can remember, every other time 3-5 points of damage). But I am absolutely sure I have never done more than 7. Maybe, since the original Guardian Halberd does 3-7 damage, the increase to 3-10 is not working?