What should I include in my confirmation letter for my DTV application to the Thai embassy?

Hello all. I submitted my DTV application via the London UK embassy this morning and immediately received this request for a confirmation letter. The thing is, in my original application documents I did already include such a letter covering the points they mentioned - it was the first page of my PDF portfolio showcasing my freelancer status. So I don’t know if I worded it wrong or it’s just that I didn’t include the Royal Thai Embassy London address as specified in their request. For anyone who has been successful with their application and was requested to include such a letter, would you be willing to share the wording you used?

I am a self-employed freelancer since 2018 and all my clients are UK/US/Europe based.

Thanks for any advice you’re able to offer!