The latency promised is obviously for the satellite segment, any DIA end user with a clue knows that terrestrial fiber latency to and from various places will vary based on where you are and how your local ISP is linked to nearby ix points and peers.
I can tell you what the latency is on fiber from the Redmond or North bend Earth stations to downtown seattle, and it's minuscule. Same as if a person was a customer on a docsis3 or GPON network in Redmond.
