Blaster,
It is 1/16" max in any location.
Mismatch (sometmes referred to as Hi/Lo) can be caused by different IDs of two pipes or a pipe may be out of round in which case the mismatch may be in only one location.
Repair of mismatch to bring it within acceptable tolerances would be up to the Engineer,
Regards,
Shane
If it says "I.D. Mismatch" then the wording means the difference between the two diameters. If it said "Internal Mismatch", then it would refer to internal surfaces. A 1/16" I.D. mismatch would be 1/32" internal mismatch all around. A 1/16" internal mismatch would be measured at any point on the inside surface and could be all around.