How are applicants answering to hidden field?

Also, I have hidden the "Shirt Size" field. Why are applicants sending in their shirt sizes?

Dear Jaime,

I have cloned your form named "Thank you for your interest in the YSN Sports Broadcasting Academy. We look forward to having you join our student body and creating life-long wonderful memories for you and your family!" on my side in order to test it. 

I have seen that you have set S option to the "Polo Shirt Size" named field by default as you can see the screenshot below:

This is the reason why the answer appears to be S in every submission despite the field is hidden as seen below:

Please set the default answer to empty option if you do not want to see that field in every submission.

I hope this helps.