How did the FCC come up with the bandwidth goals?

The FCC issued the order to adopt “as bandwidth targets, the State Education Technology Directors Association’s (SETDA) recommendation for Internet access for schools of at least 100 Mbps per 1,000 students and staff (users) in the short term and 1 Gbps Internet access per 1,000 users in the longer term. Internet connectivity will be measured at the district level for school districts and at the school level for schools that are not members of a district.”

“The Order adopts as a target for WAN connectivity the total number of schools that have a connection capable of providing a dedicated data service scalable to the SETDA long-term WAN target of 10 Gbps per 1,000 students.”

Reference: Summary of E-rate Modernization Order.  
Reference: SETDA, The Broadband Imperative.