Inconsistent definition for NERO_PROGRESS?

CoasterRoaster

In NeroAPI7.0.5.6.pdf I see:

> typedef struct tag_NERO_PROGRESS
> {
> NERO_PROGRESS_CALLBACK npProgressCallback;
> NERO_ABORTED_CALLBACK npAbortedCallback;
> NERO_ADD_LOG_LINE_CALLBACK npAddLogLineCallback;
> NERO_SET_PHASE_CALLBACK npSetPhaseCallback;
> NERO_DISABLE_ABORT_CALLBACK npDisableAbortCallback;
> NERO_SET_MAJOR_PHASE_CALLBACK npSetMajorPhaseCallback;
> NERO_PROGRESS_CALLBACK npSubTaskProgressCallback;
> } NERO_PROGRESS;

But in NeroAPI.h I see:

> typedef struct tag_NERO_PROGRESS
> {
> NERO_PROGRESS_CALLBACK npProgressCallback;
> NERO_ABORTED_CALLBACK npAbortedCallback;
> NERO_ADD_LOG_LINE_CALLBACK npAddLogLineCallback;
> NERO_SET_PHASE_CALLBACK npSetPhaseCallback;
> void *npUserData;
> NERO_DISABLE_ABORT_CALLBACK npDisableAbortCallback; /* Will be called only if the NBF_DISABLE_ABORT flags is given to the NeroBurn function */
> NERO_SET_MAJOR_PHASE_CALLBACK npSetMajorPhaseCallback;
> NERO_PROGRESS_CALLBACK npSubTaskProgressCallback; /* provide the write buffer fill level */
> } NERO_PROGRESS;

The header file shows a void *npUserData member in the the middle of the struct that's not mentioned in the API spec.

I assume the header file is correct. Can someone comment on the purpose of the npUserData pointer?

Thanks.