AND it still sees the Verbatim dual layer 4x 8.5GB as 3.99GB. The Nero info tool gives me a media id: MKM 01RD30 also at 3.99GB.
Your Verbatim MKM 01RD30 discs are of the DVD-R DL (Dual Layer) format ("dash" variant).
Your NEC ND-3500AG drive doesn't support this format - it only supports the "plus" variant DVD+R DL (Double Layer) instead (and of course also all the Single Layer formats).
You will have to get some Verbatim 2.4x DVD+R DL (MKM 001) media instead, or get a newer burner.
The DVD+R DL format is the most compatible format anyways if you want to burn video and play your disc in a DVD player.
BenQ DW1655, LiteOn LH-20A1P, LiteOn SHM-165P6S, Plextor PX-760A, Plextor PX-712A, Pioneer DVR-111L, NEC ND-4551A
Optiarc AD-7173A, Matshita UJ-840S, LiteOn SHW-1635S, LiteOn SOHR-5239V, NEC ND-3500AG, Sony RDR-HX910