Based on my boarding ticket, is my booking class E or Y? How do I know? It obviously seems to be Y but a customer service representative said it was E and am seeking retro mileage claim.

Other info---- The Korean Air service rep isn't giving me my mileage (via flight partners on Sky Team) cause they claim its E booking class. Can I call China Air to verify my booking class? Is there a definitive answer about what booking class I really have?

These are the mileage accrual rules based on the A, B, C, D whatever booking class https://www.koreanair.com/global/en/skypass/earn/partner-ailrlines/china-airlines/

The receipt is from my booking it on a Chinese website (ctrip.com) and it just translates to "economy" class without stating the letter