How accurate is respiratory rate sensor on Marq?

I am wearing my Marq adventurer last two nights and respiratory rate it shows at night get very low to 7 brpm. In the graph some point I see no data as well, has breaks. That said my range is between 19 and 7.

Is anyone else getting similar numbers? The normal rate is supposed to be between 20-12 so my 7 is very low.

I wonder how accurate is this sensor?