You are comparing the results from a Live Analysis graph and a summary graph in the Analysis Module. The difference is that one is filtered the current entity and the other is will pull from the whole project. If these test have been added to more than on Test Set, each instance will be counted. To get the option to filter by the current entity you would need to create the graph under the Analysis Menus tab -> Test Set Analysis Menu. This will also add the graph to the Analysis Menu in Test Lab.

ALM User Guide Page 705

Shows how many tests in an ALM project belong to test sets.
Specify the type of data displayed along the x-axis, and the test plan and test in test set information by which
ALM groups the data.

Note: If you create the graph in the Test Lab module, you can choose whether to include
only the current test set or all test sets.

ALM User Guide Page 792

Live Analysis graphs represent only nodes that are located directly below the selected folder. They do not
include tests, test sets, or business components located at a lower hierarchical level in child folders of the
selected folder.