u/EquivalentHopeful405

Im doing the Huebner cone 6 schedule and im noticing that while its set to hold a temperature for 10 minutes (Ex: 190 °c for 10 minutes) the tempature will continue to rise reaching 209° befor stalling and beginning to slowly cool 3-5 degrees in the remaining 5 minutes of the hold. Is this normal? Is it caused by the temperature outside? Is it broken?

Im really worried its already busted after only 2 firings and ive wasted $400+ 😓

For context, i have my kiln outside, it has sat in my garage over the weekend after 2 succesful firings, 1 bisque and 1 cone 6 glaze for test tiles.