To begin refinement, just choose a commodity from the selection in the right side of the window. Below the commodity's name you can set the amount to be created. The default amount is the maximum available which can, of course, be modified, and in case you set a higher quantity than you can afford, the available amount counter turns red.
The delta number is a measure of efficiency that shows the difference between the unattainable (100% efficiency) and your current requirements. For example, at 100% efficiency, you need 75 pcs of titan ore to create 1 piece of titanium. Any higher than 75pcs is the + delta requirement shown in red.
Fortunately, you can improve this rate in three ways. First, you can improve your relation to the facility's owner by completing assignments. Second, you can install additional refinement extensions. Third, you can search for a refinery with higher production points. It is not possible, to beat the delta and exceed 100% efficiency.
Additional parameters that affect your total efficiency.
Relation ratio - Improve this factor by reaching a good relationship with the owner of the facility.
Material ratio - Improve this factor by installing extensions that affect the material efficiency of the process. This value includes the above mentioned relation ratio.