diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 507347d..ef99ca6 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -6707,8 +6707,13 @@
 			a conversion is wider than the field width, the field
 			is expanded to contain the conversion result.
 			The 'h' modifier indicates the argument is 16 bits.
-			The 'l' modifier indicates the argument is 32 bits.
-			The 'L' modifier indicates the argument is 64 bits.
+			The 'l' modifier indicates the argument is a long
+			integer.  The size will be 32 bits or 64 bits
+			depending on your platform.
+			The "ll" modifier indicates the argument is 64 bits.
+			The b and B conversion specifiers never take a width
+			modifier and always assume their argument is a 64 bit
+			integer.
 			Generally, these modifiers are not useful. They are
 			ignored when type is known from the argument.