Ahh. I see. I took a look at the script. “Blocked Users,” is not reported by an instance, but rather It’s calculated by this script by looking at “Blocked Instances,” which is reported. How many active users each blocked instance has and then summing this together, the script shows “BU.” I was thinking it was an explicit list of users the instance blocked based on ban/block lists.
It’s a derivative, but still useful metric, I guess. BU could be high, but BI could be low and vice-versa.