Shifting data is stored in the Event message as a single 32bit value. The ‘rear_gear_num’, ‘rear_gear’, ‘front_gear_num’ and ‘front_gear’ are each 8 bit values that get packed into the Event message's 32 bit data field. Each component is then expanded in to the individual target fields for convenience so apps that decode the files do not have to. But when creating the files, you need to pack the values in to the data field.
Scroll down to the Components section here, or search the page for "front_gear", for an example. developer.garmin.com/.../
