Why do grouped graphs sometimes have extra space to the right?

The problem

Your data look like this.

Your graph looks likes this, with lots of white space to the right. In this case, there is so much white space that you can't even really see the bars that show the data. 

Why it happens

The data for this example was originally on one column of values in Prism or Excel. The data was put into Prism's grouped table using Paste Special with the setting  to put ten values on each row. 

A bug in Prism Windows up to 7.03 leaves Prism confused. It thinks twenty rows of data were pasted so it leaves room for twenty sets of bars.  In fact, while  twenty rows of data were copied, those values were pasted into only two rows. We'll fix in the next release. 

Workaround

Select the row directly below your data, and Delete. This will force Prism to rethink many rows are placed on the graph. 

An alternative workaround: Double click on your Grouped graphs, go to the third tab and tell Prism to leave 0% gap for missing/excluded values. It "thinks" there are a bunch of missing values below your data, and this will tell Prism not to leave space for them.

With either workaround, the graph will now look fine.