Information about 2-event Classification
When 2-event classification is configured and a class 4 device is detected, IOS allocates 30W without any CDP or LLDP negotiation. This means that even before the link comes up the class 4 power device gets 30W.
Once 2-event is enabled, the port resets automatically. Power budget allocation for a class-4 device will be 30W if 2-event classification is enabled on the port, else it will be 15.4W.