How to time a slide show

Hey! i really need help noooow!!! please. i’m doing a Pecha Kucha, where the slide show is suppose to change slide every 20th second. i’ve tried averything! but i don’t understand what to do. help me please

Open the slide transition effect pane. There you will find the section “Advance slide”. Select “Auto” and set the desired 12s. Press button “Apply to All slides”.

That should work, but I get some problems with the time. In version 4.2 the number means hundredth of a second, in version 4.3 it is a decimal number in seconds.