I don't know about that specific problem...

But in general and guessing as to what that might possibly mean (I could be way off!)...

When computers transfer data, there are ways to verify or "double check" that the data was sent or received without any errors. And if that happens, the data is then retransferred.

So the above could be saying the code reader you are using is not capable of 2 way communications and therefore can't *confirm* data transfers (including DTC's) are error free?

Or that new software was previously installed to the vehicle, but it was never verified to be correct?

Or there is some internal or vehicle computer to computer communication problem where the accuracy of communications can't be verified?

Sort of like with people, one person says; "My number is 123456".
The other person says; "123456?"
The first says; "Yes, that is correct!"