The flash trigger pulse time is the time the flash trigger signal is active. It is not the flash pulse. This is available to allow for old cameras. When I first started developing the dropController the camera I was using required a fairly long trigger pule to activate the shutter. Since I added the facility for the camera I also added it for the flash.
The flash pulse has to be set manually on your flash; 1/32, 1/64, 1/128, etc. The longer the flash pulse (smaller numbers) the more light you get but you also get more movement in the water and so you also get more blur.