Reports the current number of distinct services, as opposed to hosts or sessions, that are active on SSG. This counts unique service instances rather than subscriber connections to them, so it's the metric to watch when deciding whether a particular service definition is actually being used at all versus just configured and idle. If an operator retires a legacy service definition but cssgStatsActiveServices doesn't drop afterward, that's a sign some other still-configured service picked up the slot rather than the retirement actually taking effect.