Without knowing which features are being used and size of the install base, comparing numbers means nothing. E.g. if the install base is mainly using syncmirror your efficiency will drop considerably. But using dedupe and flexclone will increase it dramatically.
is the RAID-DP saving compared to RAID10 or RAID1.
It makes no difference - different vendors / people use different terms for the same thing: a set of drives with the data stripped across (for performance) & then mirrored with an identical set (for resiliency). Capacity overhead is always 100%, hence the suggestion that RAID-DP improves efficiency, whilst still being able to sustain double disk failure.