If you have multiple marketing sources that are essentially the same (maybe there was one created and was mispelled), you can combine them so that your Marketing Report is more accurate.
Click your name at the top right and go to Marketing sources.
On the left hand side you will see a list of ALL marketing sources you have in your account.
Check the box for the marketing sources you wish to change.
And on the right hand side select which source you want to change the selected to.
Confirm the change and then select "reload" when prompted.