We are given two volume values, each volume has a certain number of molecules. The second number 6.20 x10^23 corresponds to the avogadro number and is equivalent to one mole of silicon. The first number does not make a molecule, so it must be only a fraction of the molecule of silicon being measured.
That will be the diference between the two number. 6.20 x10^23 is equivalent to one molecule while 4.188x10^22 is not.
