While the 232 amp hour figure is per battery, you need to connect them in series to get 12 Volts. Adding batteries in series increases the voltage, but the amp hours stays the same, i.e. 232. Since it is not a good idea to discharge your batteries more than 1/2 way, 116 amp hours is what is available.
How many amp hours you actually have available depends on the withdrawal rate. The 232 amp hours stated in the battery specifications is at a 20 hour rate, i.e. putting a load on a fully charged battery that will completely empty it in 20 hours, or, in the case of the 232 amp hour battery, 11.6 amps. Since we don't ever want to completely empty our batteries, the actual available amp hours will be considerably less.
There is a term called the "Peukert Effect" that throws a monkey wrench into trying to calculate how long your batteries will last. Basically, the effect is that if your current draw is higher than the 20 hour rate specification, the amp hours available goes down. If you draw less, it goes up. The 20 hour rate is useful for comparing batteries, but not all that useful for determining actual run time.
For more than you will ever want to know about batteries, check the Battery University
For useful battery information for RVers, I like Mark S. Nemeth's "12 Volt Side of Life, Parts 1 & 2"