What information is needed for the invitation letter when traveling to china with a tour group?

I do not understand what I need to provide for this document since no one is inviting me.The visa service I am using states that I needed the following : a copy of the hotel confirmation and airline tickets and my tour itinerary. However the tour company I am using (China spree} does not provide this information until 3-4 weeks prior to the trip.Is the information that the visa service has given me correct. Please advise.