I would like to add, I stopped smoking back in 1999 and I an 41 years old. I exercise a lot (ardio, core, yoga) and walk to and from work (30 minutes each way) everyday. I don't feel out of breath or winded from walking.
An ordinary chest x-ray would not be sufficiently reliable for a diagnosis of what is, apparently, mild emphysema. And you have no symptoms that you are aware of....
In other words, they are saying you have mild COPD. When my father when for a CT scan (he had stomach cancer) the results mentioned dmild COPD, it was a surprise.
I believe the only way the X-Ray would show it is if your lungs are hyper inflated with barreling of the chest. Only a CT scan can be sure.
Since you have no symptoms it is entirely possible that the diagnoses is wrong. However, if you want to be sure, then visit a pulmonologist to get tested. There is, however, a simple test you can do yourself. Get a peak flow meter. These are inexpensive and can be found on the internet, but I don't know if you can get one in Korea. I uses one made by "Assess." You blow into it and it tells you how you score compared to norms of men your age and height. Because I have emphysema I have one of these meters. Most people with lung problems use them.