I don't think its as clear as you infer, pugzi. The actual regulation makes no mention of 'calculated' landing distance. It says:
(a) An operator shall ensure that the landing mass of the aeroplane determined in accordance with JAR–OPS 1.475(a) for the estimated time of landing at the destination aerodrome and at any alternate aerodrome allows a full stop landing from 50 ft above the threshold:
(1) For turbo-jet powered aeroplanes, within 60% of the landing distance available; or
(2) For turbo-propeller powered aeroplanes, within 70% of the landing distance available;
And the answer to the question lies in the interpretation of that word. 'Calculated' could mean, as you suggest, the gross LDR but it could equally well mean the net LDR, particularly as all Class A aircraft manuals have the 1.67 safety margin built into the graphs and tables so all values 'calculated' would already include that factor.
To clarify, you are allowed to use all the landing distance available but you are not allowed to plan to use all the LDA.
Flystudent, in short yes, appeal the question. It is ambiguous.