"装卸货计数人" can be translated as "cargo loading/unloading counter" or "person responsible for counting loaded/unloaded goods".
The first option, "cargo loading/unloading counter," emphasizes the role of counting during the loading or unloading process. The second option, "person responsible for counting loaded/unloaded goods," directly describes the person's duty in a more detailed way. Both translations are acceptable, and the choice may depend on the specific context or preference.