The clocks in a focus are anything but exact, in fact the majority of clocks in the entire world lose time or gain time, really no difference. Honestly I wouldn't worry about it.
Also how are you calibrating your clock in the focus? Syncronizing it with an internet based exact time? you own watch on your wrist? a telephone time call service? Keep in mind that you may be matching the focus clock to something that IS the reason for the wrong time.