exact meaning/calculation of 144 hours

I know the time starts at 00:00 hour of the day after you arrive, is it until 23:59 of the 6th day after that?

If you arrive on 22-May, then:
22 = arrive in Beijing
23 = day 1
24 = day 2
25 = day 3
26 = day 4
27 = day 5
28 = day 6 - Must leave by 23:59 on 28th? Is this correct?