> The smallest audience you can upload is an audience size of 30 people. Also, this audience size needs to be 30 people which Facebook can identify and find. So, if you upload an email list of 30 and Facebook can match only 20 of those email addresses to Facebook profiles then it will reject your list, so in most cases you need to upload a list of about 60 people. You then need ensure you upload a list of only females or males which includes the one email address of the person you are targeting (the opposite to the one person that you are targeting). Lastly you need to choose the gender in the demographic filtering which matches the intended target. Here’s a step by step example below

"Sniper Targeting on Facebook: How to Target ONE specific person with super targeted ads" https://medium.com/@MichaelH_3009/sniper-targeting-on-facebo...