Why is the amperage of a kiln higher than the rating when a kiln is first turned on?

When you first turn on a kiln and the elements are cold the amperage is higher. Once the elements heat up the resistance changes by about 4% and the amperage goes down. That is the meaning of "Hot Amperage" and "Cold Amperage" and "Hot Resistance" and "Cold Resistance".

What normally matters is the "hot resistance" because the "hot amperage" is what a kiln normally draws so this is what the electrical circuit normally sees. The "cold resistance" only lasts for a few minutes - normally under the time that a fuse or circuit breaker might trip.