diff --git a/builds/install/misc/firebird.conf b/builds/install/misc/firebird.conf
index f03392696f..0d361a0b9a 100644
--- a/builds/install/misc/firebird.conf
+++ b/builds/install/misc/firebird.conf
@@ -818,8 +818,9 @@
 
 # ----------------------------
 # Bytes of shared memory allocated for lock manager.
-# In Classic mode, the size given is used for the initial allocation. The
-# table expands dynamically up to the limit of memory.
+# The size is an allocation unit. The table expands dynamically in
+# increments of this allocation unit, up to 2 GiB - 1, or the limit of
+# memory.
 #
 # Per-database configurable.
 #
@@ -856,6 +857,8 @@
 
 # ----------------------------
 # Bytes of shared memory allocated for event manager.
+# The size is an allocation unit. The event manager expands dynamically in
+# increments of this allocation unit, up to the limit of memory.
 #
 # Per-database configurable.
 #