How do you tell the difference? If you go into a meal high, say 10mmol. You inject at your usual ratio, and two hours later your blood sugar is not higher than 13mm. Four hours later you are back at 10. Your ratio is correct. Your blood sugar still too high but your ratio is correct. You can then try a correction independent of the original bolus, which is no longer effective.
If your blood sugar is correct two hours later, then you managed to correct as well - you injected more than you needed just for the food. If your blood sugar is too LOW, you over-corrected.
The way you work this out is through trial and error. You need to write down everything to see your pattern.