A B and C error reporting are for how the error is reported. Type A turns on the light at the first error. Type B waits until a second failure is seen. Type C only reports the problem if you check with a scan tool. A code can still be stored but the check engine light won't turn on. If you uncheck the box then it won't run the test. This means the OBDII monitor won't set and dependent tests won't run either. For example, if you don't run the secondary O2 tests then the cat converter test won't run. If you select "no error reporting" the test runs and passes instantly... readiness monitors show "ready" and dependent tests run. In places where you have to do the OBDII plugin emissions test you're better off with "no error reporting." If you know the system isn't on your vehicle and there's no side effect to unchecking the box, go ahead and remove the check.