The time savings come from the fact that you don't have to write it all out yourself or go trawling through old projects copying and pasting while trying to remember which project had what. You let ChatGPT bang it out in a few seconds, which it will get 95% of it correct and you just spend a couple seconds fixing the errors.

Another way I find it useful is where I already know how to do something but can't quite remember all the little details like which Dll or class it's in or what the function names are. I tell ChatGPT what I want and it gives me what I need to fill in the blanks. Many times I just write it all myself while using ChatGPT's answer as a reference to aid my memory.