Your brain is a wonderful pattern recognition machine, and will anticipate when the next bell occurs if they come at regular intervals. In order to support a mindfulness practice, the bell is always randomized. That way it's harder for your brain to anticipate when it will ring next.
However in Lotus Bud Mindfulness Bell does allow you to influence the timing. Using the Bell Timing slider will make the random bells closer together by sliding it to the left and further apart by sliding it to the right.
This allows you to tweak Lotus Bud Mindfulness Bell for your own usage but keep you on your toes while you pursue your practice.