It's the ramp time until full fuel cut on decel, longer time, longer it takes to get DFCO. That way you get burbles, but can also still benefit from decel fuel cut.
Your car uses the same ecu structure as the Focus RS, so it will have dedicated Burble control logic within it. HP Tuners has already defined them all for the RS, so you should drop them a ticket and get them to add it for your car, unsure why they havent already. It's a far nicer way to control the burbles.