And so does every Swiss watch manufacturor who spec'ed their chronographs at 1/5 or 1/4 second. Breitling has done both over the years and continues to do so. Obviously, 3 small ticks marks between a second/minute marker divide the space into four equal parts (1/4 second chrono) and 4 small tick marks divide the space into five equal parts (1/5th second chrono). In fact, a 28,800 VPH movement (7750's, 2892's) moves the sweep chrono second hand forward eight times in a second. A 21,600 VPH movement (1873-1877) moves the sweep chrono second hand forward six times in a second. Tough for the human eye to discern the difference in either rate or spacing which dictates a specification that is apparent to the viewer when the chrono hand is stopped. (Hand width issue if nothing else.) Hope this makes sense for you. I proved the incrementation totals yesterday using a video camera with a frame time slowed to 1/4th real time in order to actually be able to see and count the "ticks" of the hand between second markers. Viewing the movement on the monitor at the reduced rate shows the number of movements ("ticks") precisely. Now the longstanding chrono incrementation issue is put to rest...
Best,
Ron
The teeth on the tilting pinion may or may not be in perfect alignment when it is brought into contact with the center wheel. This inderminate alignment can create friction as the teeth are engaged. Also, there is a certain amount of inertia that must be overcome before things start to move. All these factors contribute to the opposing force transmitted to the fourth wheel. This causes the fourth wheel to pause momentarily. 
Next I checked specs on my 21,600VPH Lemania Cossie and my caliber 22 Flyback Cossie (2892-A2 movement, 28,800 VPH) and found both marked on the dials for 1/5th second and indeed spec'ed that way in the Chronologs and Sales Handbooks. 
Something wasn't adding up. I began to research chronograph operation relentlessly and was never able to find an adequate explanation for the disparity in markings. Detailed study of the movements led me to conclude it had to be gearing ratios in the chrono train and nothing else. Still, it seemed as though the "dirty little secret" would not be revealed with research and conclusions alone. A controlled "test" was the only way to prove with finality what many of us suspected or denied. That is the reason I set up the camera and software and used four of my Breitlings as test subjects. Fortunately I have available all examples of the calibers and markings necessary to make the test conclusive and accurate. A little embarrasing for me to have to "stand corrected" from false early conclusions but lacking "finality" was nagging at me hence the decision to set up the test. Glad I did it and I hope it helps those of us who are truly intrigued by what many would consider to be trivial and unimportant. 