Hi Mike. There are three adjustments that can be made on most scopes for your particular vision.
First, is the eye relief. This is the distance from your eye to the lens of the scope and it is set by moving the scope back or forward in the mounts before you tighten them. This allows you to optimize the view you see through the tube.
Second is the leveling of the scope on the rifle. Making sure the scope is level allows the image to transmit through the lens of the scope accurately.
Third is the eyepiece focus. Focusing the eyepiece ensures the reticle sharp and clear for your eyes. This will vary from shooter to shooter. The eyepiece is the rear lens of the scope and can be screwed in or out depending on your vision. Typically the younger the shooter's eyes, the further in the eyepiece is adjusted, the older the eyes, the further out you will find the setting to be.
Hopefully this will help you understand the adjustments. Here is a great article on the subject from one of the world's best optic companies. Enjoy. https://www.leupold.com/leupold-core/core-knowledge/articles/how-to-adjust-your-riflescope
Ross