A "full carry" in industry terms always means carry to first oil. After that the party that was carried though the exploration and development process pays its share of the costs to produce each barrel.
A full carry also means that there would be no deduction by Addax, once oil is produced, of the amount it paid to cover ERHC's postion of the exploration and development costs.
Therefore ERHC only pays its portion of the production costs once oil is found in commercial quantities.