OK, I now understand.
If you select Category (with NO tag selected): Автоматические высокопроизводительные широкоформатные рулонные резаки you see all the products that belongs to this category. This is 4 results.
If you select the Tag (with NO Category selected, which means all categories are used): APR Solutions you see ALL THE PRODUCTS of the company APR Solutions. This is 9 results.
With OR relationship selected, you then create a VENN diagram of results, where the results total must be minimum of (max of 4 and 9 is) 9 and maximum of 13 (add 9 + 4) results in theory. In this case there are 13. This is the expected behavior of OR operators in programming searches.
If you wanted just the 9 results, then Category must be set to ALL instead when selecting a Tag, which means you would need to create some javascript to do this when a tag (other than All tags) is selected.