Specifying an destination offset for cudaArray in cudaMemcpy3D

Dear fellow CUDA programmers,

in the documentation for the parameters of cudaMemcpy3DParms it is emphasized that

The destination object must lie entirely within the region defined by dstPos and extent.

However I am not quite sure as to how this statement has to be interpreted.
Does this simply mean that “dstPos + extent <= extentDestination” or that “dstPos + extent == extentDestination” ?

This is assuming I am using a cudaArray for dstArray in cudaMemcpy3DParms.
I do get a return code from cudaMemcpy3D indicating a successful operation and it seems to work as intended, however I would like to make sure I properly use the API to prevent future.

Best regards