SDK is used on online go servers for Single Digit Kyu (9k to 1k) usually considered as intermediate strength players
DDK is used for Double Digit Kyu (beginners start at 25k on OGS to 10k)
Please don’t focus too much on ranks. Ranks are made to get interesting pairing with players of similar strength so producing interesting games for both.
It’s not really for bragging and the best players keep some modesty even before the existence of over powered AIs
It looks like your fantastic question offers a lot of room for interpretation!
I was truly honored to play, learn, and be guided by Queen of Light (what an incredible name!) in that fair-as-real-life game.
Just as @Groin said, we are all like round stones playing. No name, no title nor race nor genders nor ages. Like all little kids, having fun.
On the other hand, my actual rank was 52Kyu and I was in top 1% (bottom up) then. So I decided that my left brain needs to practice with math, intensively, to balance with my dreaming right brain.
We can reach specific goal more easily if it is specified in numbers, isn’t it?
Another Certificate granted by ChatGPT and SORA: Here it is as a token of gratitude to all of my fellow OGSers, who have taught me various lessons about Go, and Life!