does 4.7gb mean 4.7gb?

[c.pugwash]

when i buy a 4.7gb dvd disc, surley it means i can put a 4.7gb movie on it, or does it?. when reading the guides they keep saying the movie must be less than 4.36gb, WHY?

[Baldrick]

A single layer DVD(DVD-5) fits 4 700 000 000 bytes and that is 4.37 "computer" gigabytes where 1 kilobyte is 1024 bytes. 4 700 000 000 / 1024 / 1024 / 1024 = 4.377216.

[c.pugwash]

so if the video_ts and the audio_ts combined, is less than 4.377216gb i can burn that to a dvdr?