always return float, update doc

lib/private/helper.php

@@ -274,7 +274,7 @@ class OC_Helper {
 	/**
 	 * Make a computer file size
 	 * @param string $str file size in human readable format
-	 * @return int a file size in bytes
+	 * @return float a file size in bytes
 	 *
 	 * Makes 2kB to 2048.
 	 *
@@ -283,7 +283,7 @@ class OC_Helper {
 	public static function computerFileSize($str) {
 		$str = strtolower($str);
 		if (is_numeric($str)) {
-			return $str;
+			return floatval($str);
 		}
 
 		$bytes_array = array(