Using to class="" attribute with an element is wrrong.
If we want to use multiple class names with an element, we use one class attribute and we use space between the class names
For example:
Without class
<span></span>
With 1 class name
<span class="class1"></span>
With 2 class names
<span class="class1 class2"></span>
With 3 class names
<span class="class1 class2 class3"></span>
To use multiple class names you need to add space between the class names, and if there is no space between them that mean there is one class name
1 class name
<span class="class1class2"></span>
2 class names
<span class="class1 class2"></span>