This is the increment size, in kbps, by which this tunnel's auto-sizing logic adjusts its reservation on each resize step, and per the description always reads 0 on a backup-role tunnel. An admin sets a smaller increment for gradual, low-disruption growth versus a larger increment when the tunnel needs to catch up to demand more quickly, trading resize frequency against the size of each individual adjustment. For example, an increment of 5000 (5 Mbps) means this tunnel grows in 5 Mbps steps each time auto-sizing determines an increase is needed, rather than jumping straight to its maximum.