One of the important factors when brewing espresso is the brewing time. Ideally, 25-30 ml (single-strainer) or 50-60 ml (double-strainer) is reached within 25 seconds. The built-in brewing timer automatically stops the brewing process after a defined time and even if you are not standing at the machine, you do not have to worry that the brewing process will take too long and the espresso will be watered down or the cups will overflow.
A note: It cannot always be assumed that the exact same amount of espresso is extracted just because the timer is used. This can have different causes: Coffee grounds that have been lying in the dead space of the grinder for a few hours, more or less coffee grounds or a shower screen that is too tightly woven (e.g. from IMS).