in my logbook i have total flight time, IFR flight time, Night flight time, PIC, co-pilot, instructor, IF flight time and Nav time.
the total time tells me my total hours.
my IFR total times tells me how many hours i have flown within my total time.
my Night time tells me how many night hours i have flown within my total time.
the same goes for each of the other times i can log. note that it is not a double entry into my logbook. IE- if an IFR flight lasts for 5 hours i would log total time of 5 hours, IFR time 4hrs 50min (taxi time removed) and night flying as say 2hrs 30min if i took off before sunset and landed at night.
if i look at my logbook in the future and see this flight i would read it as it was a 5 hour long flight wich consisted of 4hrs 50min of IFR flying and also consisted of 2hrs 30min of night flying.
when flying VFR, night flying is conducted under IFR rules but your actualy flying under SVFR.