One time exception meaning?

I bought an iPhone 6s back in July and by october the phone was dying at 20-30%. In November Apple replaced the device after my 2nd visit and checking the phone's usage logs showing the phone was dying early. Now it is February and my replacement device has begun to die at around 20% as well. It also has a bright dot on the top left of the screen(dead pixel?) which is prominent in white background. I was transferred to a senior advisor and she said she put a "one time exception" on my case number. What does this mean?