GCSE mark equivalent - help me understand please

[Teencrisis]

DS got a 5 for his biology and his mark equivalent was 85. I thought that meant that out of the 2 papers he scored 85. This would mean that he was 1 mark off a 6. I’ve asked for his papers and the joint score was 83. I am now really confused. What does a mark equivalent mean?

It probably means that the scores to calculate the grade are UMS rather than the raw scores.

With the 86 for a 6, I presume he did AQA with Biology as a stand-alone science?
Both papers are marked out of 100. What did he get on each?

@Testina he got 48 marks in paper 1 and 35 in paper 2.