Think of it this way - in an atom, the number of protons = the number of electrons, and protons and electrons have equal but opposite charges. This means the resultant charge of an atom is 0, atoms are neutral.
As two electrons have been lost, this means that there are 2 more protons than electrons in the atom, so it is now an ion. Therefore the charge of this ion is the same as the charge on 2 protons (the same as the charge on 2 electrons, except positive as the atom has lost negative charge)
Does this make sense?