Delay generation?

Thanks for the suggestions, even though I can’t work on it all the time, I’ll put all the tips aside, (I didn’t forget that the “hight” text is still wrong!).
However, this time it is not clear to me why to put a delay in the optimization. I could do it in cron, but I don’t understand the benefit. The conversion system for a single image is very fast, at least on my sites where I use it. Even if I load a dozen images together it converts them in a few moments.
If you can help me understand I would appreciate it.