16 * 108 = 1728. Chant each round with counter.
One has to hear one's own voice. This video is just to give a feeling of chanting with Prabhupada. Prabhupada would chant with devotees in the temple hall but everyone would hear their own sound. That's called JAPA!

Note: This is NOT the actual time which Prabhupada used to take for chanting one round. This is just the average time which a wakeful person takes to chant one round. One can chant at one's own speed. 7 mins 25 sec (time taken for one round in this video) is NOT THE HARD AND FAST RULE!
Prabhupada would chant faster than this!

how to chant hare krishna
hare krishna mahamantra
chant with prabhupada