Clarified what happens if the interval is small. See RT #130168

Author: Jan-Olof Hendig

doc/Type/Supply.pod6

@@ -238,7 +238,9 @@ to be only executed by one thread at a time.
 
 Creates a supply that emits a value every C<$interval> seconds, starting
 C<$delay> seconds from the call. The value is an integer, starting from 0,
-and is incremented by one for each value emitted.
+and is incremented by one for each value emitted. Note that if the supplied
+interval is less than one millisecond it will be changed to one millisecond
+and a warning will be emitted.
 
 =head2 method grep