You have a main process with a Process Call shape. There are multiple return paths from the process shape but only one is expected.
This is expected behavior (see Return Documents shape). A Process Call shape will have a return path for each Return Documents shape present in the subprocess. This allows you to use different Return Documents shapes in the subprocess to represent different possible outcomes. The Return Documents shape labels are used as the return path labels.
For example, you could design the subprocess to encapsulate error handling or validation logic and send documents to one of two Return Document shapes labeled as "Valid" and "Rejected". The main process then can simply handle each path appropriately.