- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks how much time is left on a loss of control that locks you out of abilities of the spell school you choose, compared with the number of seconds you set. If no such lockout is on you, it does not match.
Why you might use it
Compare how long one school of your spells stays locked out, as after an interrupt such as Counterspell, Kick or Pummel. A Mage whose Fire school is locked can switch to Frostbolt until it returns, and any caster can bring spells of another school to the top while the main one is blocked. It reads only your own character, so it works on every edition, Retail included. See also Loss Of Control Type and In Control.
Example
time remaining on block of your Fire abilities is greater than 0 seconds
Settings
What each setting in the condition editor means, from the game's own help.
School Blocked - The type of ability you are prevented from using.
Operator - How to compare Loss Of Control Blocked with the Seconds value. This comparison uses basic mathematical comparison operations.
Seconds - How long until the loss of control expires.