fix sm

doc/modules/mod_stream_management.md

@@ -90,9 +90,9 @@ Stream management state data is stored under the `mod_stream_management` key in
 The state data record, `sm_state`, has the following fields:
 
 * `buffer` - buffered stanzas not yet acked by the user
-* `buffer_size` - number of messages buffered for the user
-* `counter_in` - number of messages on the server and not acked by the user (server's `<h>`)
-* `counter_out` - number delivered to the user and acked by the user (user's `<h>`)
+* `buffer_size` - number of stanzas buffered for the user
+* `counter_in` - number of stanzas received by the server (server's `<h>`)
+* `counter_out` - number of stanzas delivered to the user and acked by the user (user's `<h>`)
 * `buffer_max` - server's capacity for buffering
 * `ack_freq` - how often the server requests acks
 * `peer` - in case of stream resumption, the `ejabberd_sm:sid()` identifiying the old session, or `gen_statem:from()` identifying the new session.