How to filter wrong matches?

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I use matching_to_many_image sample to find one image among multiple.

const string defaultDetectorType = "SURF";
const string defaultDescriptorType = "SIFT";
const string defaultMatcherType = "FlannBased";

It works perfect and finds query.png among train images:

Image0: 0%; matches: 0 of 538
Image1: 0%; matches: 0 of 538
Image2: 100%; matches: 538 of 538

Problem is when I don't add query image or something same to train I get this:

Image0: 62.2677%; matches: 335 of 538
Image1: 37.7323%; matches: 203 of 538

Of course it's wrong matches but I don't understand how to filter them. Please help me. How to get 0% match like in first example?