If your chart data values are not so much different from each other, the chart created using this data will not help your audience to differentiate the series representing those values.
To learn more, choose your version of PowerPoint. If we do not have a tutorial for your version of PowerPoint, explore the version closest to the one you use.
Microsoft Windows
Set Minimum and Maximum Values on Value Axis in PowerPoint 2013
Set Minimum and Maximum Values on Value Axis in PowerPoint 2010
Apple Mac
Set Minimum and Maximum Values on Value Axis in PowerPoint 2011
Tutorial Code: 10 08 03
Previous: 10 08 02 Axis Titles in PowerPoint
Next: 10 08 04 Tick Marks in PowerPoint