upload_size_limit_filter( int $size )

Source

File: wp-includes/ms-functions.php

function upload_size_limit_filter( $size ) {
	$fileupload_maxk = KB_IN_BYTES * get_site_option( 'fileupload_maxk', 1500 );
	if ( get_site_option( 'upload_space_check_disabled' ) ) {
		return min( $size, $fileupload_maxk );
	}

	return min( $size, $fileupload_maxk, get_upload_space_available() );
}