Your first year clump has surpassed all that we have grown in all the years. I believe I got about 10-12 tubers from the record holder for us but it had a much smaller clump. HH Miss White makes a bit above average tubers. Your seedling looks to grow tall like Miss White. 
The 2020 seedling went open center the next year but we are still growing it. Margaret has theory that someone would buy it despite being open center.
Most of our first year clumps have about 3-4 tubers. To be honest, I am glad our first year clumps are rather small as I only want a few tubers to grow it again, not 10-12 and harvesting clumps like this is back breaking.
We are still digging but will be done soon. Digging clumps is not an easy thing to do when you are in your mid 70s. Yesterday, I set a goal of 6 rows but after 5 rows, I was "too pooped to pop" to use 1950s slang.
