{text_title} title_length Not Working

Hi,
My args using post_html inside {text_title}.
But title_length args not working.

<?php
$args = array(
    'wpp_start' => '<ul class="list-group list-group-flush post-number">',
    'wpp_end' => '</ul>',
    'post_type' => 'post',
    'limit' => 5,
    'range' => 'all',
    'post_html' => '<li class="list-group-item"><a class="h6 h6-md h6-lg" href="{url}">{text_title}</a></li>',
    'title_length' => 20
);

wpp_get_mostpopular($args );
?>