From 0 to 20g it is 2 euro; from 20 to 50g is 2.40 euro, and so on. Nopcommerce applies a "per gram" price, that is nonsense in my opinion.
go to admin -->configuration -->all settings find (probably page 11) ShippingByWeight.CalculatePerWeightUnit and set it to false
Also a "rest of the world" option in the calculation by country - it is impossible to set a shipping for every country in the world
you currently have a shipping method for your country - go to configuration --> shipping --> shipping methods and add a new method called 'rest of world' - save and go back to shipping methods list
you will see a new column appear in the country restrictions list - beside the writing ''rest of world' tick the checkbox
now go down this column to Italy an untick the checkbox beside it - click save ( at top of page )
you have just created a shipping method that will apply to everyone outside Italy ------------ in your italian shipping column ( the one you had at the beginning), make sure Italy is ticked and all others are unticked click save
more than this, when you edit your shipping method computation method, you can choose to limit the shipping options which are presented to the customer (ie they will not see italian shipping prices if they are from France or anywhere else)
to extend its use further, you could specify european countries (i know from the uk shipping to europe is cheaper than shipping outside europe) and then 'rest of world' to create three different sets of options )