Difference between single_tier, two_tier and two_tier with EO

[Marco Cesareo]

Reading in the documentation and online I understood that the single tier considers edge servers and mobile devices. In the two-tier architecture, mobile devices can send their activities to the global cloud using the WAN connection. It's right ? If yes, then why in example 1, in the two tier scenario does the average service time and average process time also calculate the edge? Thanks for the reply.