Good espresso in the cup is a balance between following three variables (in addition to the requirement for chemical and mineral free water, non-oily medium roast beans).

1- The fineness of the coffee grind (powdery fine for non-pressurized filters and granular grind like the fineness of table salt, for fully automatic models). 

2- The quantity of coffee grounds used per shot  of espresso. (minimum 7 gms. maximum 9 gms.)

3- The quantity of water per shot of espresso (1/2 oz. for Ristreto to 2-oz. for good espresso).

All of the three variable factors need checking and adjustment to improve the quality of espresso. 

Grind adjustment

The adjustment of knob setting at (8) is what is called the factory setting. After use over several months that can change and may need adjustment. There is no standard setting where it will automatically make the best espresso. The adjustment should begin where the position of the knob is.

That is what is the starting position of the knob. After adjusting the grind, the dose of beans per shot of  

The adjustment of the finesness of grind in Italia is done by using the knob on the rear right inside the bean hopper. Turn (clockwise) to higher numbers for coarser grind. Make sure that the grinder is working when grind fineness is being adjusted. This is especially so when the finer grind is desired.

Always change the grind one notch at a time. Check the result of change by inspecting the discarded coffee puck. It should be well formed like a hockey puck.

The three factors that change the quality of espresso is the fineness, the quantity of ground coffee per shot and a well formed puck.

A well formed puck is possible only when the fineness and quantity of coffee fill the compacting cup as desired.

Over filled cup can damage the brew drive gears.

Under filled compacting cup will show gooey or watery puck.

Extra coarser grind will have a fragile puck that easily breaks as it falls into the dump box.

Too fine grind will have watery pasty puck as finer grind takes less space in the compacting cup.

With the three factors balanced, the last and final evaluation will be to check the dark color of espresso and the thickness of crema. For correct evaluation and setting the quality of espresso for its color and thickness of crema, use shot glasses. The narrow mouth of shot glasses will accumulate crema for judging its thickness.