Weapon (greatsword), uncommon
You have a +1 bonus to attack and damage rolls made with this magic weapon.
Proficiency with a Greatsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.
This weapon has the following mastery property. To use this property, you must have a feature that lets you use it.
Graze. If your attack roll with this weapon misses a creature, you can deal damage to that creature equal to the ability modifier you used to make the attack roll. This damage is the same type dealt by the weapon, and the damage can be increased only by increasing the ability modifier.
Notes: Bonus: Magic, Damage, Combat, Heavy, Two-Handed, Graze
Does this mean just one or both damage dice get the +1? Basically is it actually adding 2 damage to every hit?
It adds 1 to the entire hit
It adds +1 to the damage roll (I believe things are added to the roll last when calculating damage)
But it also adds +1 to the attack roll to see if you hit the attack.
So really it only increases the damage per hit by 1, but it increases the DPR by significantly more than that due to the increased hit chance.