Automatic kilns and even manual kilns shut off by the use of cones are never as accurate as the human eye. 99.999% of time this is fine.
When in doubt it is almost always better to fire slower than faster.
A slower firing allows for more time for water vapor, fumes and gasses to escape from the body of the clay body.
The first thing to check is to make sure you are not putting on too thick a layer of glaze.
After your kiln has fired press the REVIEW PROGRAM button.
Specifically this error code means that during a cooling segment in the programmed firing, one of the thermocouple temperatures is more than 50 degrees above the set point for longer than 1
On the Easy-Fire e28T-3 kiln (and School-Master SM28T-3) you will find the cone rating is limited by the KW of the kiln.