6.—(1) Paragraph (2) applies only if regulations 2(2) and 2(3) result in more than one issue of the Standard or version of a Guidance Note being current during the Annual Operation in question and, if they are treated as separately current for the whole Annual Operation, this yields different efficiency percentages for the purposes of regulation 3(2).
(2) The efficiency percentage in regulation 3(2) is then the weighted mean of those different efficiency percentages.
The weighting must reflect the proportion of fuel input to the station during the period in relation to which the relevant issue or version is current.
That proportion must be calculated relative to the station's actual total fuel input for the Annual Operation in question.