ANSWER
Please find hereafter the answers to your two questions relating to the meaning of the 3rd indent of the paragraph 1(c) of the Art. 23 of Annex II (General Conditions) of the model contract "Cost reimbursement for research and technological development", which is the following:
Article 23 - Direct Costs
1.Personnel
(c). "For contractors using the additional costs system, costs shall be limited to the actual costs of the personnel employed on the project (gross remuneration and related charges) where the later has concluded: - ...
- ...
- a contract which depends upon external funding additional to the normal recurring funding of the contractor. In that case, the costs charged to this contract must exclude any costs borne using such recurring funding".
Your two questions:
"1- What is the meaning of the "external funding" and the "normal recurring funding of the contractor" in that case?""2- Which of the above expressions refer to the funding obtained from the European Union under the specific project?"
A researcher may have a contract which depends partly on external funding.
In other words, the working contract of this researcher mentions explicitly that a part of the salary of the researcher is subject to its involvement in specific activities financially supported by external funding (like the financial contribution of the Community to an indirect action of the Framework Programme).
This part of the salary of this researcher, but only this part, is considered to be an additional personnel cost that could be reimbursed at 100% (only for participants using the AC cost model). | 
