What’s problem if I forgot to enter my middle name?

What’s problem if I forgot to enter middle name in my visa application?

I completed visa on arrival application and received the visa approval letter yesterday. However, I have just found that I missed my middle name. What problem if I my middle name is missing in the visa approval letter?
You will need to enter the information correctly as it appears on your passport when you apply for Vietnam visa. Please do not miss any part of your full name and do not miss (or enter incorrectly) any letter or figure of your passport number. If you forgot to enter your full name or you entered information incorrectly, you may be NOT allowed to get on the plane to enter Vietnam. Even you are allowed to get on the plane, you will be stopped at the visa counter at arrival airport.
In this case, please submit another visa application as soon as possible and kindly remember to provide your full name correctly.
If you don’t have much time, you may use the urgent service fee from www.e-visasvietnam.com to receive new visa approval letter in 1 – 2 working hours and pickup visa at arrival airport.