When you show slide numbers in a presentation, they appear at the bottom of each slide. Numbers are updated when you change the order of the slides. Skipped slides aren’t numbered.
You must be in navigator or light table view to add slide numbers.
Select the slides you want to have slide numbers.
Shift-click to select contiguous slides, or Command-click to select any set of slides.
In the Format inspector, select the Slide Number checkbox.
To show slide numbers for all slides in your presentation, choose Slide > Show Slide Numbers on All Slides (from the Slide menu at the top of your computer screen).
To hide slide numbers, select the slide or slides with numbers, then deselect Slide Number.
To hide slide numbers for all the slides in your presentation, choose Slide > Hide Slide Numbers on All Slides.