TTL in auth plugin

Hey everyone I want to ask for help because I’m trying to implement TTL on auth keys however it works strange and unpredictably for me. I don’t understand why adding TTL sometimes changes creation date of key I also don’t understand how Kong calculates this remaining ttt? Is the ttl connected to creation date or it leaves alone? Why sometimes it is impossible do update ttl value and sometimes it works. When exactly is the point from which Kong starts count down the ttl?