This status induces countdown induced death, very much like FF5 and 6.
The status counts down from whatever the initiated value happens to be (which is 10 for Count/Doom spell).
It can be affected by Stop (and Dispel can remove Stop under this instance, strangely enough).
This status is totally unaffected by Haste and Slow... so those of you that assume that the Plague "hurts you" by casting Haste on you are totally wrong. In fact, the only reason it doesn't hit is due to high magic evade. (Like Evil/Wicked Mask's Reflect on you on the SNES version).
The attack itself has a perfect hit rate of 100%, but it's completely unblockable. It is has the boss-bit set.. so it can't be used on bosses.
Interestingly enough though, it is reflectable. FF2/4ET has the Fataleye/Ahriman monsters that don't have the boss bit set, so you can see the monster die from Count.
Testing Count status on enemies is interesting.. only two "designated" monsters are only able to be declared as "Count inflictable"... there are some odd bugs that go with this.. as when there are 2 or less monsters with the status inflicted, the game could freeze in attempting to remove them. The game is actively waiting for a command (by either monster or character) to be executed so Count's auto-death stuff can be done. You will also notice that the monsters inflicted with this status eventually don't attack anymore. The only safe commands to use are magic, item, change/row commands..
Edit: Note, the 2 monster limitation seems to be specific to the monsters groupage that can cast it.. which is a pair of Fataleye/Ahriman.