How to send variable int count from one blueprint to another?

I have an ammo blueprint that holds a certain amount of ammo of a certain type (as an enum) and I would like for it when I call a function in the BP_Ammo to be able to add that ammo to a global ammo count of that ammo type. Im not quite sure how to do this. I tried storing the values in my GameInstance bp but that didnt work, and Ive tried using a interface but Im not sure how that is supposed to work. Any help?

Is it a multiplayer game? What blueprint do you need to access that data?

It’s single player, and I have an ammo blueprint that when is triggered, adds it’s ammo count to the total ammo count of that ammo type to the players weapon inventory. I don’t want to have to create the ammo variables in the player blueprint though, and I can’t directly access my weapon base blueprint that contains the ammo type it it’s outside of the player blueprint on its own.