Clarify how Latest Object works the the Largest Object is incomplete

Fixes: #592

Author: afrind

draft-ietf-moq-transport.md

@@ -1494,10 +1494,15 @@ There are 3 types of filters:
 Latest Object (0x2): The filter Start Location is `{Largest Object.Group,
 Largest Object.Object + 1}` and `Largest Object` is communicated in
 SUBSCRIBE_OK. If no content has been delivered yet, the filter Start Location is
-{0, 0}. There is no End Group - the subscription is open ended.  Note that due
-to network reordering or prioritization, relays can receive Objects with
-Locations smaller than  `Largest Object` after the SUBSCRIBE is processed, but
-these Objects do not pass the Latest Object filter.
+{0, 0}. There is no End Group - the subscription is open ended.  
+If an implementation has published or received the beginning of a new `Largest
+Object` but not the end, it can choose either this "current" Object or the
+previous `Largest Object` to create this filter.  If it chooses the previous
+value, the current Object passes the Latest Object filter, and it MUST be
+delivered starting from the beginning. Note that due to network reordering or
+prioritization, relays can receive Objects with Locations smaller than
+`Largest Object` after the SUBSCRIBE is processed, but these Objects do not pass
+the Latest Object filter.
 
 AbsoluteStart (0x3):  The filter Start Location is specified explicitly in the
 SUBSCRIBE message. The `Start` specified in the SUBSCRIBE message MAY be less