WordPress at a glance
function is not described

WP_User::level_reduction() public WP 2.0.0

Choose the maximum level the user has.

Will compare the level from the $item parameter against the $max parameter. If the item is incorrect, then just the $max parameter value will be returned.

Used to get the max level based on the capabilities the user has. This is also based on roles, so if the user is assigned the Administrator role then the capability 'level_10' will exist and the user will get that value.

{} It's a method of the class: WP_User{}

No Hooks.

Return

Int. Max Level.

Usage

$WP_User = new WP_User();
$WP_User->level_reduction( $max, $item );
$max(int) (required)
Max level of user.
$item(string) (required)
Level capability name.

Changelog

Since 2.0.0 Introduced.

Code of WP_User::level_reduction() WP 5.7

<?php
public function level_reduction( $max, $item ) {
	if ( preg_match( '/^level_(10|[0-9])$/i', $item, $matches ) ) {
		$level = (int) $matches[1];
		return max( $max, $level );
	} else {
		return $max;
	}
}