The capacity of a DVD

[parsifal]

Well, I was not sure where to post this topic... perhaps this is more flame than support related topic ... But hopefully it fits among others.

I am new to the whole DVD-burning world. I went shopping and bought a box of five Fujifilm's supposed-to-be-standard-DVDs, size 4.7GB. I got home, inserted one of my new DVD+R-discs and got terrified: the size of the DVD was actually 4483MB.

Let's see if I can calculate this one correctly...

1024B equals 1kB.
1024kB equals 1MB.
1024MB equals 1GB.

Therefore 1GB equals 1024*1024*1024 B = 1073741824B.
That multiplied with the factor 4.7 = 4.7 *1073741824B = 5046586572.8B

And that divided with 1024 to get the size in kilobytes:
5046586572.8B / 1024 = 4928307.2kB
And megabytes:
4928307.2kB / 1024 = 4812.8MB.

4812.8MB - 4483MB = 329.8MB

Of the 4.7GB disc this is: 329.8MB / 4812.8MB * 100 = (approximately) 6.85%

It is a big difference.

If any of the following is true, jump to the end of my post :
- I am in a dire need of mathematics class (the obvious choice)
- DVD-burners can't burn over 4480MB (I'd still like to know why the capacities are overstated)
- File system eats the missing 300MBs (how can it?)
- something crucial I haven't noticed

To many this may seem like a whining of a no-lifer, but to me, there are few reasons to get upset with this:
1) I need the whole announced capacity of 4.7GB
2) I really hate to pay the prize of a 4812.8MB disc and get a 4483MB disc

Why is it so? Is this a standardized lie, that is OK to make customers pay 6,85% extra for capacity that is not there? When buying a CD-R, I know it can take the 650MB/700MB of data, no less. Or I (should) get a refund. It's a funny world if customer has to know the specs if he want's not to get lied to (too often it is, I guess...)

Any clarification would be welcome.

Thank you.