While observing the new stats counters ( https://grafana.wikimedia.org/d/eemh00uzqj6yoc/edge-uniques-drilldown ) and manually testing various artificial / invalid cookie values against production, I realized that we don't have a distinct statistic for the case of "The cookie was sent, but the length of the cookie value was wrong".

Currently, if the cookie value is completely missing/empty, it's counted as c_fresh_null, and if it has a value of the correct length (64 bytes) but something else is wrong with the value, one of several distinct errors are counted (such as c_fresh_invalid_b64, c_fresh_invalid_mac, etc). But if the cookie value exists and is the wrong length, it's added to the same counter as the empty/missing cookie case.

We should probably have a distinct stat on this condition! It can roll out with the next version bump once it's ready. No need to hold back rollout over this (it's not a behavioral issue, just a stats counter issue).