This update is a Penguin 3.0 follow-up that was released as a result of the many issues caused by Penguin 3.0 and multiple complaints made by website owners.
As with any penguin update, this update’s purpose is to address website over-optimization as well as inbound link issues.
This update is a ‘fix’ to the earlier Penguin 3.0 update, so if your website was affected by this update it’s recommended that you check your website’s status before and after Penguin 3.0 in order to draw conclusions and decide on your next move.
Since this update was observed by website owners and wasn’t officially announced by Google – there is no information on the percentage of queries affected by this update.