Real Arousal Index / RERA?

On my sleep study i have two sections:

Arousals Respiratory arousal w/o dsat: 4.1hr Respiratory arousal w dsat: 2/hr

But my RERAS are scored as 0 on my analysis. Are RERAS and the two statistics above different? My RDI is scored the same as my AHI because my RERAS were all set as 0.

Thanks in advance