Question about ranked 3s ranking system

Hi all! So I know at the beginning I started at grade 20 worked down to grade 1 and flipped to tier 1 or whatever. Now I’ve noticed the rankings have changed again and I’m tier 10. I’ve also noticed limit rankings or something as well. Where can I find a full list of the current rankings or does anyone know how the ranking structure is currently built? Was just curious cause going from tier 1 to tier 10, didn’t know if I’m doing good or poorly.