Start with the feet in the down position and back off the foot pressure. Measure the height of the inner foot at it's highest position. The feet operate inversely from eachother, so let's say you get 8mm. You need to give 4mm to the other foot to even them out. In the back of the machine, you should have an adjustment shown here.
Where the arrow is pointing, you will see either a hex bolt or allen bolt. Loosen this bolt and pivot the cam (circled) until you achieve closer to 4mm height, then tighten the bolt. Once tightened, cycle by hand and compare the heights of each foot. You will not get it just right the first time, most likely have to do it several times to get it right where you want it. And as stated, they should be as close to equal as reasonably achievable. Hope i'm making sense.