Are there Tutorials out there where you can pull a total amount of ammo from a specific ammo from grid or slot like inventory?
I hope not, that would a pretty badly designed system. The UI should not be counting bullets, its job is to display stuff. Have the inventory actor / component count what’s needed. Besides, since you’re already displaying numbers in the UI, you’ve already counted it all, surely… How else?
And if you really must do it this way, iterate over the slots checking what’s inside and add it up.