What does j9T mean in yescrypt (from /etc/shadow)?

Consider this Shadow string

$y$j9T$PaFEMV0mbpeadmHDv0Lp31$G/LliR3MqgdjEBcFC1E.s/3vlRofsZ0Wn5JyZHXAol5

There are 4 parts - id : y (yescrypt) - param : j9T - salt : PaFEMV0mbpeadmHDv0Lp31 - hash : G/LliR3MqgdjEBcFC1E.s/3vlRofsZ0Wn5JyZHXAol5 **Q:** 1. What does j9T in param field mean? 2. Are there other options in this field? 3. Where can we find official documentation? I've seen this question; The format of encrypted password in /etc/shadow , however, there is no explanation there.