If you are working on a presentation that will be part of a bigger presentation, it doesn’t always work out well to use the default slide numbering in PowerPoint. Let’s say that your boss wants you to prepare 15 slides that are to be included in a major presentation. Your slides will be numbers 10-25. If you use the default, then your slides will be numbered 1-15, making it rather confusing if the boss wants you to change slide number 12. Does he mean his slide 12 or your slide 12? To keep everyone on the same page, you can change the starting slide number for you presentation to better meet your needs.
1. Go to the Ribbon and select the Design tab.
2. Click Page Setup.
3. Use the Number slides from box to select the desired number to begin your slide numbering.
4. Click OK.
So if we wanted the slide numbering to begin with the number 10, we would place 10 in the Number slides from box. This would change what we see from this:
To this: