Hi Kell:
The NCSU supplemental requests that you list contacts from which you did not receive official eLORs for your VMCAS. That being said, the number of contacts on the supp will depend upon your particular circumstances (i.e. what type of experiences you listed on your VMCAS app). If you listed an veterinary/research experience on VMCAS (from which you did not receive an official eLOR) this experience needs to be mentioned on the NCSU supplemental in the form of a 'contact.' NCSU gives you the option whether or not you want this individual contacted, and gives you a small space (i.e. about 75 characters) to explain why you don't want them contacted, if this is the response you chose.
I had 7 'contacts' listed on my NCSU supp. I am 34, and have worked in a variety of environments for a number of years. Of those 7, I requested that 2 not be contacted because I have not been in contact with these individuals for multiple years. I also mentioned (in the tiny space available) that I do have proof that the experience took place. NCSU has plenty of options available to contact my other references (in both the form of official eLOR, as well as other experiences listed) to get a feel for my experience range and suitability for the veterinary profession.
If you list an experience on VMCAS (and do not obtain an official eLOR), you do not have the option to 'opt out' of including the 'contact' on the NCSU supp. If you don't want the individual contacted, say so in the space provided (that's why it's there). Admissions folks are human- they know that every experience can't be golden. Also, there are those of us that are older and have been the workforce for a number of years. One of the experiences I listed dates all the way back to high school! That being said, if you think the contact would really reflect poorly on you, you have the option of removing the experience from VMCAS entirely. I personally wouldn't go this route.
Good luck.