The warring triad (the three goddesses) on the floating continent.

A quarter a dozen, the problem of all
chaos contained, within in the wall
With the slightest bump, it will fall.

Quarter of a dozen --> there are three of them.
the problem of all --> just what it says
chaos contained --> The balance of the three of them is what keeps things contained, "balanced" as in the World of Balance.
within in the wall --> not a hundred percent sure what this line means.
With the slightest bump, it will fall --> when Kefka moves the statues out of alignment, the Floating Continent falls.