OK. Economics is three papers, 100 marks each - but
they're not weighted equally. According to the specification
here:
Paper 1: 100 marks: 35% of the total qualification
Paper 2: 100 marks: 35% of the total qualification
Paper 3: 100 marks:
30% of the total qualification
To make the 100 marks in Papers 1 and 2 "worth more" than the 100 marks in Paper 3 they must weight them. The specification doesn't actually mention they weighting they use, which is odd. However,
if they used a weight of 1.125 for Paper 1 and Paper 2, then the 200 marks from Papers 1 and 2 would be "worth" 225 marks (i.e. 200 x 1.125). Add that to the unweighted 100 marks from Paper 3 and you get the 325 marks they claim.
With those weightings (i.e. 1.125, 1.125, 1.000) that would make each paper worth 34.6%, 34.6% and 30.8% of the total exam - which is pretty much what they say in the specification. They might be weighting them slightly differently to this, but this is essentially why you're seeing that odd raw mark.