See AGMA 923-B05, Table 2 as a guideline. The allowable IGO (intergranular oxidation) depth is dependent on the specified case depth. The highest allowed is 60μm for 3mm case depth. Yours appears to be pretty bad, but it all depends on what case depth you're working to.
ISO 6336-5(2003), Table 5 also has similar requirement.
IGO is always checked in the as-polished condition