STYLE: update notes about patch level on development branches

- previously stated that the patch level would be 0, but this would
  necessitate many revert commits after merging in the master branch.
  It is better to leave the meaning open.

META-INFO/README.md

@@ -44,7 +44,6 @@ source archives.
 
 - 6-digit year-month-day (YYMMDD) integer corresponding to a patch-level
   for the given **released** API.
-  Development branches have a patch value of `0`.
 
 - Format is year-month-day, as per `date +%y%m%d`.
 
@@ -53,6 +52,9 @@ source archives.
   day, the patch level would jump accordingly.
 
 The patch value is only meaningful together with the api value.
+However, for *development* branches, the patch level should not be
+ascribed much meaning -- it can be `0` or have a value corresponding
+to the last merge with a *maintenance* (*eg*, `master`) branch.
 
 
 ## Flow of information
@@ -81,4 +83,4 @@ contains more permanent information, whereas the `build-info` is more
 transient in nature.
 
 ----
-2018-11-29
+2019-01-23