BYOND Version:N/A (Website Bug)
Operating System:Linux
Web Browser:Firefox 12.0
Applies to:Website
Status: Unverified

Thus far we've been unable to verify or reproduce this bug. Or, it has been observed but it cannot be triggered with a reliable test case. You can help us out by editing your report or adding a comment with more information.
It appears that there's some sort of caching in affect with hub entries that causes the server counting and actual server listing to become desynched. I built a simple world to demonstrate this issue:

world/hub = "Audeuro.TestHub"
world/visibility = 1

var/old_visibility = world.visibility
var/new_visibility = !old_visibility
world.visibility = new_visibility

world << "Visibility toggled from [old_visibility] to [new_visibility]"

The first bug I noticed was when I hosted it on my VPS as well as the Tibbius server, then closed out my VPS's instance. The server listing showed both servers open while the server count went down to 1, as opposed to 2. The second one is certainly directly related:

I put up my world, then toggled visibility from 1 to 0 once. It changed, as expected, and the server listing reflected that and the # servers was accurate. I then toggled it again from 0 to 1 and the server appeared again, everything was right. This is where everything started to go sort of haywire, as far as I could tell. Toggling it once more caused the # servers to drop to 0 but the server listing still showed my server, as in the screenshot. Toggling it again from 0 to 1 caused the # servers to go back up to 1. After that, changes in visibility had no visible effect.

I then took that world down to refresh the hub entry. After everything was updated accordingly, I put the server back up. This time I couldn't get changes in visibility to affect the hub entry at all, the server remained visible through thick (0) and thin (1).

I discovered this while investigating another possible bug with world.visibility itself, but the unpredictable behavior of the hub entry made it impossible to determine anything from my testing.

Additionally, I have used CTRL+F5 in Firefox every time to refresh the page in an attempt to eliminate browser caching from the problems.
Some of this could be hub reporting, which would be at the software end, but the inconsistency you're seeing between the values reported is definitely a website issue.
Lummox JR changed status to 'Unverified'
I tried to get this to happen but was unable to replicate the discrepancy shown in your screenshot. Hiding the server made the game count show 0 and did not show the server in an individual listing anymore, as it's supposed to, and showing it again reverted it to normal list of just a single server with a count of 1.