Originally posted by eMule FAQ
Credit System
The credit system is used to reward users contributing to the network, i.e. uploading to other clients.
The strict queue system in eMule is based on the waiting time a user has spent in the queue. The credit system provides a major modifier to this waiting time by taking the upload and download between the two clients into consideration. The more a user uploads to a client the faster he advances in this client's queue.
The modifiers are calculated from the amount of transferred data between the two clients. The values used can be seen in the client's details dialog. To view this information, right click on any user and choose View Details.
There are two different credit modifier calculated: