Kröger-Vink notation for defect reactions
Yes, the Kröger-Vink notation you are asking about, implies that the metal has lost or gained one electron, relative to the case of the perfect crystal. This situation can be explained by non-stoichiometry. 

A non-stoichiometric compound is one of which the proportions of the atoms can not be represented by integers.
Consider the case of $\ce{Fe}_{0.95}\ce{O}$. Indicated by the subscript 0.95, there are some metal atoms missing, which is expressed as the defect $\ce{$V$^{''}_{Fe}}$. This has a double negative charge, which can be compensated by 'replacing' $3~\ce{Fe^2+}$ by $2~\ce{Fe^3+}$ ions. That is, 2 iron ions need to be oxidized and 1 needs to disappear.

This can be accomplished by dissolving $\ce{Fe_2O_3(s)}$ into $\ce{FeO(s)}$, as in:

$$\ce{Fe_2O_3(s) -&gt;[FeO] 2Fe^{.}_{Fe} + 3O_{O} + $V$^{''}_{Fe}}$$

Alternatively:

$$\ce{2Fe_{Fe} + 2O_{O} + 1/2 O_2(g) -&gt;[FeO] 2Fe^{.}_{Fe} +3O_{O} + $V$^{''}_{Fe}}$$

More examples are described in my source, chapter 11 of the book 'Ceramic Materials' by Carter &amp; Norton.