Those sealey supermigs come with a very basic and inaccurate regulator. I used to set mine to 10 lpm on the dial but when I swapped to to a BOC regulator & a flow meter I was surprised how much more flow I was getting at the nozzle for the same setting on the flow meter.
Has yours got 1 or 2 gauges?
Has yours got 1 or 2 gauges?