Russian language for groups didn’t work

According to your help – https://conditional-fields-cf7.bdwm.be/conditional-fields-for-contact-form-7-tutorial/

I’ve changed English titles of groups to russian lang.
After that – select drop-down menu didn’t show any Russian lang. title

example :
———–
[group Заказ магазина]
Выберите модель: [select* operating-system first_as_label “– План запуска? –” “Мини” “Макси” “СРедний” “Windows”]
Please specify your OS version: [text version]
[/group]
———–
screen 1 – https://www.screencast.com/t/vCZFo70HF67a
screen 2 – https://www.screencast.com/t/2IyFzUUM
is it bug ? or only English language is available for your plugin?