Yes, Your Phones are Spying On You

I know Alexa listens to more than what follows the word, "Alexa"

If you said a sentance like.. "I think I will ask Alexa."

The think light comes on at the word Alexa, but then goes out within a second"

if you say "Alexa"

The think light stays on for 5-10 seconds waiting to hear a question.

This means that in order to ignore the first example, it had to have context from what came before it heard "Alexa".
Just how much is it recording? (or what defines temporary voice buffering?).