rms

My JBL 305p MKii's sell sheet telling this ↓ What does it mean?

Hello there, I have a question. I'm going to calibrate my Kali-Audio LP6 in an acoustically treated room. I will use -20 dB rms pink noise. How I imagine this process - I will place SPL-meter on a "sweet-spot", and then calibrate every monitor individually to -83 dB. My audio-interface is...