[ECI-EN] Tolerance of proofing substrate color

I have a question about proofing ISO 12647-2:2007 (or Fogra 39). The color of the print substrate used for proofing shall be in tolerance dE <= 3 with the color of the print substrate used for production (for example according to Media Wedge proofing process). My question is: which document (and section) is this value of dE <= 3 specified? 12647-2 Table 1 specifies tolerance not in terms of dE but individually in terms of dL, da, db. There is perhaps another document or another section? Can you help me? Thank you. Mauro Boscarol