When the label on a DVD+R states that it holds 4.7 gigs, that's a load of crap--they're counting a 1000 kilobytes as a megabyte, and a 1000 megabytes as a gig. In reality, its 1024 KB to a MB, and 1024 MB to a GB. Doesn't seem like a big deal, until you encode something to 4.7 gigs in size, and you find that you can't fit in onto a DVD+R.
So always be careful, and use the correct definitions of the terms, as that's what Windows and all the encoding and burning programs use.