DVD size questions !!

[JonRead]

I am a bit on the confused side. How much excactly, down to the last MB, can be fitted on to a DVD-R ? It says 4.7gb on the label but only 4.3gb can be recorded ? Some software seems to allow 4.4gb. I just used Instant Copy to backup a 7.4gb DVD and it shrunk it down to 3.9gb for some reason when it could have gone up to 4+ gb.

So can someone explain the exact amount ? Especially due to using the cutom option in Instant Copy. Should I take the red bar warning as correct if I set it to 4.4gb, or are they (the software writers) just playing it safe ? Also what is the point in labelling it 4.7gb ?

Sorry the newbie style questions.

[Zhnujm]

for cd/dvd/hd manufactures:
GB = billion bytes

for a computer:
GB = 1024*1024*1024 bytes

so:
4,7 billion bytes : 1024 = 4589843 KB :1024 = 4482 MB :1024 = 4,37 GB

thats the cause of the difference.

(not that it hadnt ansered many times before... ;))