total timing = base timing + KC + other timing compensations (ex. IAT, ETC, etc.)
KC = (timing advance map value * IAM(raw value)/16) + feedback knock correction + fine learning knock correction
So, KC is basically another compensation to base timing. It is more useful to log the three elements of KC separately by using Enginuity's logger and latest logger definitions. Logging KC alone, especially if you don't know what the advance map for the particular tune looks like, isn't as useful.
As you can see from the formula above, KC can be positive even if there is negative correction due to knock. So, just looking for negative KC isn't useful in determining knock. That is why logging the individual elements of KC gives you a lot more information. You will typically see negative KC at low loads where the advance map value is zero, meaning any negative correction will cause KC to be negative. Obviously, negative KC at moderate to high loads is a great cause for concern considering the advance map value will be a positive value, meaning that there is a lot of negative feedback and/or fine learning correction.