THM Astral Fire/Umbral Ice stacking
Will someone explain in detail how do Astral Fire and Umbral Ice stack?
The Magick and Mend level 20 trait reads: Increases base action damage and HP restoration by 10% and allows for the stacking of a second Astral Fire or Umbral Ice.
Now, I understand that Astral Fire makes your Fire-related attacks stronger and Umbral Ice give you an MP regen, but what I don't understand is the "stacking" part.
Example: When I use Fire I see the Astral Fire buff, when I use Fire again, I see the buff icon has "II" on it. I just don't understand what it does exactly or how to use it.
Does it just mean that it's more potent? Example: Fire attacks are even more stronger and MP regen is even more after "stacking"
Thanks in advance :)