If you notice a significant change in your subscriber count within the next few days, don't be alarmed - this is due to a fix we are running to rectify a bug which has affected subscriber counts on some users' channels. Normally, when a user subscribes/unsubscribes from your channel, this change is reflected in your subscriber count almost immediately. We discovered an issue which was preventing these numbers from being updated. We expect the fix to take just a few days to reach affected accounts. Once it is complete, everyone's channels will reflect the current and accurate number of subscribers.

Thanks for your patience,

The YouTube Team