how to remove overlap of cost element in allocation structure?

hi experts,

on KSES the source has double entry of cost element. those cost elements were defined under cost element group. when i checked on the Source screen the entries under the cost element group there is no double entry but when checked on Extras > Overview List i can see two entries of the cost element. how can i remove on the double entry of cost element on the source of the allocation structure?

thanks!