This is often a bit confusing, because a DVDR is not 4.7gb.
The confusion comes in because the manufacturers label them in kilos i.e. 4700,000,000 bytes.
To get a true conversion you have to divide by 1024 to get kilobytes (4589843) then by 1024 again to get megabytes (4482) and then by 1024 again to get gigabytes (4.37).
So, no .... you're disks are fine, it's just terminology.
When Erwin(Dvd20ne) recommends 4400, he is talking megabytes and as you can see, this leaves 82megabytes free, as a safeguard.
Hope that makes sense m8