This graph is displayed on accessed issue page. That issue is the root for graph (1). At the beginning this graph displays only links of pointing to and from root issue.
It is however possible to load more issues that are indirectly linked with root issue by expanding issues. If issue is expanded, it means that all its links are displayed. At the beginning only root issue is expanded. In order to expand an issue double-click on it and all its links will be loaded. Expanded issues have blue background (1) (except root issue which has violet). Expanded issue can be collapsed by double-clicking on it. Collapsing an issue means hiding its links. Collapsed issues have grey background (2). At the beginning all linked issues are collapsed.
...