From AMule Project FAQ
It stores up to 5 sources, no more. To decide between all the available sources which ones to choose it takes the following priorities:
- Sources which are currently actively downloading the file to us
- Latest found sources, since they might be the hardest to find and, since they have been the last ones found, they are the most bound to be active on next session.
Seeds storing can be enabled in Preferences -> Files -> Store 5 seeds for rare files.