Hey Zenith,
There are several reasons for this:
1/ Visits from FB editors and FB bot
2/ On FB if someone comments or share your post, you can get organic traffic from other countries you're not paying for (even though I believe it's not your case according to the stats you shared)
3/ Different way of detecting countries between FB (most accurate) and your aff network. For example, some platforms detect me as coming from Romania while I'm located in UAE.
And probably a few others...
Friends of people liking, commenting and sharing your ad located in different countries.
=)
every campaign gets a small part of its entire volume from other countries, thats normal. you just have to make sure you have a solution in place to monetize these worthless visits (other country, carrier, language, etc). theparkingplace.com and rookmedia are good solutions for this.