In my Football Retention file, I decided to duplicate the GradYrSchoolYr worksheet, intending to substitute Grade for school year. The new sheet is called GradYrGrade.
The problems began when I added Grade to Columns and removed School Year. Grade is a discrete dimension (School Year is continuous), and making the change to Grade shrunk my chart horizontally and made the data markers in the line chart giant. I then changed Grade to a continuous dimension. That corrected the chart size and got rid of the giant data markers, but created other problems: I could no longer use the aliases for Grade (7th Grade, 8th Grade, etc.) and limiting the axis to 7th Grade through 12th Grade left no room for the labels at the beginning and end of the lines.
I decided to work with the shrunken chart and giant labels. First, I dragged to right edge of the chart to get it sized correctly, which made my giant data markers even bigger. Next, I went to the sum(players) area of the markers tab (the axis for my data markers) and clicked on the Size square. That brought up a little slide bar that I could use to properly size my data markers.
I also discovered that by single clicking on my line labels, I could move the labels so they weren't overlapping. It's a little daunting because it also brings up a dialog box. Just ignore that and focus on the moving symbol to move the label to the right spot.