Panasonic Optical Zoom amounts

Hi. I have been wondering this for a while, can anybody tell me how exactly the "EX OPT Zoom" affects the focal length of a lens? Of course I know the lens's focal length does not change, but what is the equivalent field of view?

I am looking for figures, for example when EX OPT Zoom is used with an M image size, the 20mm's FOV will look like a 30mm (for example), or the FOV is multiplied by 1.5x (for example).

Thanks.