diff --git a/promises/lib.php b/promises/lib.php
index 463cd16..56f42c4 100644
--- a/promises/lib.php
+++ b/promises/lib.php
@@ -2,6 +2,12 @@
 
 namespace Lib;
 
+/*
+php.ini
+
+precision = 16
+bcmath.scale = 6
+*/
 function microtime_calc(): array
 {
     static $last = null; // 1st time