*UDF 1.02 as first released UDF revision is know by most implementation on the market. It is used for DVD-Video for instance. UDF 1.50 defect management makes it the usual choice for CD-RW, DVD+RW and DVD-RW (except MRW, as they do have defect management at hardware level) . File streams of UDF 2.00 allows to have multiple stream per file, like on NTFS. ACL and power calibration are optional features not used by InCD. Real Time Files from UDF 2.01 is useful for streaming, for instance video streaming. The metadata partition from UDF 2.50 regroups the metadata information (information about files, directory and the volume in general) in a partition on the media, so both (read) access is faster and a duplicate of this information is possible (with sector-to-sector match so a recovery software can re-build the information even if both partitions are partially damaged).*
The above was taken from a Nero Forum.
as for the capacity issue the formatted size of a standard (ie not Dual Layer) DVD -R is calculated as follows 2,298,496 sectors == 4,707,319,808 bytes == 4489.25 MB == 4.384 GB I cannot find the number of sectors on a DVD RW