Why is there a problem with the output through sprintf in Wordpress?

Question

WordPress

I am modifying (using existing code) the LearnPress plugin so that the certificate displays the grade instead of percentages.
By analogy with the function of displaying the results in percentages, I made the output function in points.

public function get_mark_result() { 
    $premark = $this->get_percent_result();
    $mark = $premark * 1.2;

    return apply_filters( 'learn-press/user/course-mark-result', wp_sprintf( '%s', $mark ) );
  }

If format in sprints is '%s%%', then the result with a percent sign is output to the certificate. If I change it to %s, then the certificate is empty, but in the console I see the result as a number.
The data itself is superimposed on the image template, parsed and converted into its part using the fabric.js script.