Convert Top 10 count to use k, m and bn

tptn-restyle-count.php

<?php
/**
 * Modify the display the tptn counter to show k and m instead.
 *
 * Add this code to your theme's functions.php file or in a file in mu-plugins.
 *
 * @param   $string $input  Formatted list count
 */
function tptn_restyle_count( $input ) {

	$input = filter_var( $input, FILTER_SANITIZE_NUMBER_INT );
	$input = number_format( $input, 0, '.', ',' );

	$input_count = substr_count( $input, ',' );

	if ( $input_count != '0' ) {
		if ( $input_count == '1' ) {
			return substr( $input, 0, -4 ) . 'k';
		} elseif ( $input_count == '2' ) {
			return substr( $input, 0, -8 ) . 'm';
		} elseif ( $input_count == '3' ) {
			return substr( $input, 0, -12 ) . 'bn';
		} else {
			return;
		}
	} else {
		return $input;
	}
}
add_filter( 'tptn_post_count_only', 'tptn_restyle_count' );