Update readme

Author: danpaz

README.md

@@ -45,8 +45,9 @@ parameter | required? | values | description
 key | type | description
 ----|----|----
 `legCount` | integer | Number of legs in the route
-`legIndex` | integer | Zero-based index of the leg containing the step; together with `legIndex`, this option determines whether an arrival instruction indicates which waypoint the user has arrived at
+`legIndex` | integer | Zero-based index of the leg containing the step; together with `legCount`, this option determines which waypoint the user has arrived at
 `formatToken` | function | Function that formats the given token value after grammaticalization and capitalization but before the value is inserted into the instruction string; useful for wrapping tokens in markup
+`waypointName` | string | Optional custom name for the leg's destination, replaces `"your {nth} destination"`
 
 `formatToken` takes two parameters: