Yes I meant to say 75% instead of 30%. However the mileage received is not far off what it should be. It depends on how BA work out the mileage needed for each sector given his itinerary.
If you break the while trip into four sectors and give 75% of the difference between J and F on the one sector it's not a kick in the arse off of the figure MileageMaven received although probably still short of a few miles I suspect.