The sign of δ g predicts whether the formation of the products in a reaction is favored. if the value is positive, the formation of the products in a reaction is:

That symbol represents the Gibb's free energy. It is a criteria for spontaneity. When its symbol is negative, that means that the reaction is spontaneous; meaning the products side is favored. When its symbol is positive, the reverse, reactant side, is favored. Therefore, if positive, the formation of products is non-favorable.