anchor.diff:      <th width="10%">Count</th>
       <th>Students</th>
     </tr>
  -  <% @levels.each do |lvl| %>
  +  <% @course.levels.each do |lvl| %>
         <% lvl_stds = lvl.user_courses.student.where(is_phantom:false) %>
  -      <% if lvl_stds.size > 0 %>
  +      <% no = lvl_stds.count %>
  +      <% if no > 0 %>
             <tr>
               <td><%= lvl.get_title %></td>
  -            <td><%= lvl_stds.size %></td>
  +            <td><%= no %></td>
               <td>
  -              <% lvl_stds.each do |sc| %>
  +              <% lvl_stds.first(20).each do |sc| %>
                     <%= render partial: "user_courses/short_name_display",
                                locals: { user_course: sc } %>
  +              <% end %>
  +              <% if no > 20 %>
  +                  <a href="<%= course_level_url(@course, lvl) %>">more...</a>
                 <% end %>
               </td>
             </tr>
  
positive.code:     <th width="10%">Count</th>
      <th>Students</th>
    </tr>
    <% @achievements.each do |ach| %>
        <% std_ucs = ach.user_courses.student.where(is_phantom: false) %>
        <% if std_ucs.size > 0 %>
            <tr>
              <td><img src="<%= ach.icon_url %>" /></td>
              <td><%= ach.title %></td>
              <td><%= std_ucs.size %></td>
              <td>
                <% std_ucs.each do |uach| %>
                    <%= render partial: "user_courses/short_name_display",
                               locals: { user_course: uach } %>
                <% end %>
              </td>
            </tr>
  
negative.code:     <td>Training</td>
      <td>
        <select id="select-training">
          <%= @course.trainings.each do |asm| %>
              <option value="<%= course_stats_training_path(@course, asm) %>"><%= asm.title %></option>
          <% end %>
        </select>
  