The Gap width within a chart is the space between two series points — this by default is set to 150% of the width of individual Data Series (columns). Usually the gap width is automatically calculated based on the chart data and the Plot Area. The space between two series’ points will be very narrow if there are many data series, or very wide when there are few data series. Even then, there is scope for some change in the gap width — you can quickly increase or decrease this width.
Learn how to adjust the gap width within charts in PowerPoint 2011 for Mac.

