The pump sends hydraulic fluid to both jacks at the same time, so the side with least resistance extends first (the other may extend more slowly). When the first jack encounters resistance as it touches the ground, the other jack will start moving (or move faster). Once both are on the ground the coach will begin to rise.
Dan already answered you correctly and just wanting to echo what he says. The hydraulic fluid is being sent to the jacks needing it most until it is equalized and then they will lift evenly. You can use the "extend" button the front wall or your remote and the action is the same. You will see the same action when in "Auto Level" as the jacks are deployed and until they are all on the ground. then as the pressure is directed to one or the other to do the leveling, the lifting is done as needed.
I had two requisites to buying my coach that it have a king size bed and auto leveling. without either one, NO deal was good enough. The 6 pt leveling system is a marvel of engineering and has worked flawlessly with one minor exception...... when the site was so uneven the nose could not be lowered enough once the jacks bottom out, it will not auto level. That's actually working correctly because unless it can achieve the perfect level, it will default and shut down.
I heard of others having trouble with these in cold weather but I would guess you could find a fluid that has a viscosity for cold weather OR heat the reservoir with a blanket that would help that. Of course what is in the legs will be cold but surely there is a solution to that problem but all others are isolated and should not reflect on the total reliability of this system. I'll never have another coach without it.