Subsequent encounter means you're seeing the doctor again for the same problem. So if you got sucked into a jet engine and lived somehow you'd probably be seeing the doctor a bunch of times, and the second doctor visit and all later visits would be encoded as "subsequent encounter"
I love weird icd 10 codes, my favorite is V91.07, burn due to water-skis on fire. Like has that ever actually happened? If so please post link, I must know.