When we used this command on our server with 20000 parameter it displayed only one grid with around 24k blocks. I myself own a grid with 80k blocks which wasn't listed. I am also aware of existing grid with 40k blocks.
Vanilla grids list (alt+F10) shows around 6 more grids that have more than 20k blocks (some of them my be bug result but i am still sure about 2 of them have more than 20k blocks)
When we used this command on our server with 20000 parameter it displayed only one grid with around 24k blocks. I myself own a grid with 80k blocks which wasn't listed. I am also aware of existing grid with 40k blocks.
Vanilla grids list (alt+F10) shows around 6 more grids that have more than 20k blocks (some of them my be bug result but i am still sure about 2 of them have more than 20k blocks)