Heyo! Thanks for the question! Gonna note this too.
Basically think of it as a d6 roll of advantage or disadvantage. If you have advantage, flip again, and if you get a single success you succeed. Disadvantage is the opposite way, and reduces your advantage by 1 per stage of disadvantage.
Say I do +3 advantage with my weapon, but because of something, I also have 1 disadvantage. That reduces to 2 advantage, meaning I flip two coins, and if any of them are heads, I succeed.
On the flip side (lol), if I have 0 advantage on a weapon, but now have 1 disadvantage, I flip 2 coins, and if any of them are failures, I do not succeed.
I need to go back and explain this because I can easily see how this can be confusing without a proper explanation. Thank you for your patience! <3