Why models from Blender has more verticles, than they really has?

I have an model in Blender with 56 vertices. But after exporting it to FBX and importing into Unity, it says that there is 217 verts. I don't quite understand that stuff, maybe it happens because faces in my model are made of square polygons, and while Blender breaking them into triangles it duplicates verts?

Converting quads to triangles doesn't add vertices. Vertices have to be split on hard edges and UV seams; what you see in Blender isn't what the model actually needs to be displayed by 3D hardware.