Dartmouth Interview Help

Hello thank you for the help in advance,

When I was checking my email today, I had noticed that I received an email from 9 days ago about setting up an interview with a Dartmouth alumni. They wanted to set up an interview on the 13th or 14th of Januray but I had not seen the email until today, and so I haven’t had the chance to respond. How badly will this affect my chances of getting in? (Note: They also gave the option of the 20th as well) I just am worried that because of my lack of response, they will have a bad impression of who I am as an applicant. Also does everyone who apply get an interview or is it based on those who they see as being worthy to schedule an interview with? Any advice is greatly appreciated.

Just apologize for not responding sooner and set the interview up for the 20th.