diff --git a/pages/ch_libconfig.md b/pages/ch_libconfig.md
index 79da993a..e214414d 100755
--- a/pages/ch_libconfig.md
+++ b/pages/ch_libconfig.md
@@ -961,8 +961,8 @@ Table 13.6. psg_client library configuration parameters
| Either a name of service (which can be resolved into a set of PSG servers) or a single fixed PSG server (in format "host:port"). | **`[PSG]`**
**`service`**
**`NCBI_PSG_SERVICE`** | string | "PSG2" |
| How often to query LBSM, in seconds. Less or equal to zero means no rebalance based on time | **`[PSG]`**
**`rebalance_time`**
**`NCBI_CONFIG__PSG__REBALANCE_TIME`**[a](#ch_libconfig.TF.psg_client_library.1) | double \>= 1.0 | 10.0 |
| How often to query LBSM while no servers discovered, in seconds. Less or equal to zero means `rebalance_time` is used instead | **`[PSG]`**
**`no_servers_retry_delay`**
**`NCBI_CONFIG__PSG__NO_SERVERS_RETRY_DELAY`**[a](#ch_libconfig.TF.psg_client_library.1) | double | 1.0 |
-| Number of internal I/O threads. | **`[PSG]`**
**`num_io`**
**`NCBI_CONFIG__PSG__NUM_IO`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 1 | 1 |
-| Max number of sessions (TCP connections) per server per I/O thread. Each thread has one session per server at start. New sessions are added dynamically (up to the limit) if all existing ones are full. | **`[PSG]`**
**`max_sessions`**
**`NCBI_CONFIG__PSG__MAX_SESSIONS`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 1 | 1 |
+| Number of internal I/O threads. Each thread has one session (TCP connection) per server at start. New sessions are added dynamically (up to the 'max_sessions' limit, see below). | **`[PSG]`**
**`num_io`**
**`NCBI_CONFIG__PSG__NUM_IO`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 1 | 1 |
+| Max number of sessions (TCP connections) per server per I/O thread. Each thread has one session per server at start. New sessions are added dynamically (up to the limit) if all existing ones are full. For a single-server service the limit is at least 2. | **`[PSG]`**
**`max_sessions`**
**`NCBI_CONFIG__PSG__MAX_SESSIONS`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 1 | 1 |
| Maximum number of concurrent streams per session (TCP connection) | **`[PSG]`**
**`max_concurrent_streams`**
**`NCBI_CONFIG__PSG__MAX_CONCURRENT_STREAMS`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 10 | 100 |
| Maximum number of concurrent submits per "on queue" callback. Essentially, maximum number of requests to be sent per one I/O operation. | **`[PSG]`**
**`max_concurrent_submits`**
**`NCBI_CONFIG__PSG__MAX_CONCURRENT_SUBMITS`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 1 | 150 |
| Maximum number of concurrent requests per server. | **`[PSG]`**
**`max_concurrent_requests_per_server`**
**`NCBI_CONFIG__PSG__MAX_CONCURRENT_REQUESTS_PER_SERVER`**[a](#ch_libconfig.TF.psg_client_library.1) | integer \>= 100 | 500 |