Animating zooms

I'd like to try doing a zoom into the Mandelbrot set for a talk that I'm doing in January. I know to use exponential on the magnification. Is there a rule of thumb for the spacing of key frames? Any helpful tips?

What's the meaning of the 90.8% in the image below? The number is mostly in the 90s, but I've seen it as low as the 40s.

This seems to be the progress on the current frame.

That's right. And regarding your first question, there is no specific requirement on where to place key frames. You can create a great zoom just with one key at the beginning and one key at the end.

Previously there used to be a problem (in UF5) with doing very deep zoom animations and you had to use multiple key frames to prevent this, but I've fixed this in UF6.