In the settings you can change the method of selecting the VAT rate:
or enter it manually
or by selecting the rate according to the chosen country.
Automatically, based on phone settings, select the language of the application, you can change it manually via the settings. Available two localizations: Russian and English.
VAT rates are provided for 62 countries. The data are taken from Wikipedia.
The application contains advertising, thus it must have more permissions.
When you first start should go to the settings and select your country, as well as interface language, if you do not automatically select approached.