So I don't use the ammo tracking automation but I don't remember that being an attribute. Ammo in the inventory gets set with the Use as a resource checked and gets put into that repeating resource section with the kinda weird class_resource, other_resource, repeating_resource_left, repeating_resource_right section. Then those repeating resource values get decremented when the ammo name matches. It's listed on D&D 5e character sheet page documentation in the section at the bottom about the companion script with some more step-by-step things to check.