and gently move it inside the vent, between the egg and the skin, in a circular motion. The vent will relax and open. You can tell if there is any membrane in front of the egg as you touch it with the probe. The egg feels rather rough or a little gritty. But if it feels slippery or slimy, then there is membrane there, and you have to start over until you are in direct contact with the egg. At that point, you can gently guide it out (when it is as close to the vent as in that photo), both with a small amount of pressure behind, and by grasping it with a forceps to pull with a gentle twisting motion. If you get the first one out, the others may begin to move down on their own.
For more details, please read the egg laying chapter in the Cornsnake Manual or the Comprehensive Owner's Guide.
Good luck!