clarify limiter functionality

python/README.md

@@ -637,6 +637,12 @@ Use cases of sealing include:
 Define limits of value amounts of tokens that individual addresses can
 hold.
 
+Limits are inclusive; a limit for 42 means transfer resulting in a token
+balance \_higher\_ than 42 should be rejected.
+
+A return value of 0 indicates that the token is categorically not
+accepted by the holder.
+
 #### ERC165 Interface identifier
 
 23778613