This is a counter/gauge tracking how many times this transmit-stats object has been refreshed with a new sample set. A stalled update value (one that stops incrementing) while timeCollected also stops advancing is the concrete signal that stats collection for this specific interface has broken, rather than that the interface has genuinely gone silent. An update counter frozen at the same value for an extended period, despite the server on the other end clearly still passing traffic, points to a stats-polling failure specific to this interface rather than an actual traffic drop.