Dear Ms. Seneerat,
As pointed out, invitation period in Korean has revised 2015 to 2016.
Attached is revised invitation letter of yours.
I apologize for any inconvenience this clerical error has caused.
I will do my best to see that such errors do not recur.
If you have any further questions,
Please don't hesitate to contact me
Thank you for your cooperation.
Yours sincerely,