Address velocity is how often one account has looked up the same address inside a window — the signal that a signup flow which keeps seeing one address, or a checkout that receives the same delivery point under fifty names in an afternoon, is looking at one person or one script rather than fifty customers.
What Spaw answers
seen_by_you is an object on every billed address lookup: count, how many times your own account looked the address up inside the window before this call, first_seen_at, when the first of those was, and window_days, seven by default. The first lookup answers zero; a repeat the seven-day marker serves free still counts, because velocity is about your traffic, not about what was charged. The counter is kept under the premise digest — the same key premise_key carries — or a hash of the folded input when the address names no building, never the address itself, and the window closes from its first sighting so a steady trickle cannot keep one alive for ever.
What it does not mean
It is your account's own lookups and nothing else. An address seen a hundred times across other customers answers zero for you: a postal address is where somebody lives, and there is no cross-account address reputation at Spaw and never will be. The guest demo and the five test addresses answer null. It carries no weight; what a count of three in a day should mean is a rule for your shipping policy or your own code, not for the score.