The nut pointing down in your pic is a lock nut. Crack it and inside that nut will be a bolt/screw that adjusts the pressure. Turning in will increase pressure (from memory). Tighten locknut when set.
It essentially adjusts a bypass in the pump head.
Try adjusting the screw clockwise first with out cracking the lock nut , with my procon pump there is no need to crack the lock nut ,from memory I think one turn clockwise will give an increase of approx 1 bar in pressure,
Thank you guys, as soon as the pressure gage arrives I'll give it a go. I know the pressure is low but not by how much.
How much is it supposed to be considering I'll do a static pressure test and not the real pressure whilst extracting?
I have my pressure set at 8.5-9 bar static at the group handle pressure gauge .