Update api-reference.md

Author: dgearhart

map-matching/api-reference.md

@@ -252,7 +252,7 @@ Each `matched_point` may include:
 | `begin_route_discontinuity` | The boolean value is true if this match result is the begin location of a route disconnect. This value will not exist if this is false. |
 | `end_route_discontinuity` |  The boolean value is true if this match result is the end location of a route disconnect.  This value will not exist if this is false. |
 | `distance_along_edge` | The distance along the associated edge for this matched point. For example, if the matched point is halfway along the edge then the value would be 0.5. This value will not exist if this point was unmatched. |
-| `distance_from_trace_point` | The distance from the trace point to the matched point. This value will not exist if this point was unmatched. |
+| `distance_from_trace_point` | The distance in meters from the trace point to the matched point. This value will not exist if this point was unmatched. |
 
 ## Get better results