What is the difference between a completed inbound call and accepted call legs?
Any call can have more than one leg associated with it (see the section: Understanding call legs).
Completed inbound calls is the count of whole calls that reach a completed status, which does not necessarily mean an agent answered the call. For example, voicemails are counted as complete. For more information, see the article: What is a completed call in Zendesk Talk?
Accepted call legs is a count of individual agent calls that connect with the end user. There can be more than one accepted call leg per completed inbound call if more than one agent connects with the end user, like in a call transfer situation.