Derrida did not have access to the signifier Creal (Créel in French) therefore he could not do better than distinguish two types of Real. Here his real as non-negative inpossible is a formulation of the Creal, while the objective and dicretizable real is what should be called the Real. This Derrida quote is taken from the excellent chapter by Pheng Cheah in the collective book New Materialisms.