Update event_cache_size and global_factor configurations documentation (#17071)

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changelog.d/17071.doc

@@ -0,0 +1 @@
+Update event_cache_size and global_factor configurations documentation.

docs/usage/configuration/config_documentation.md

@@ -1317,6 +1317,12 @@ Options related to caching.
 The number of events to cache in memory. Defaults to 10K. Like other caches,
 this is affected by `caches.global_factor` (see below).
 
+For example, the default is 10K and the global_factor default is 0.5.
+
+Since 10K * 0.5 is 5K then the event cache size will be 5K.
+
+The cache affected by this configuration is named as "*getEvent*".
+
 Note that this option is not part of the `caches` section.
 
 Example configuration:
@@ -1342,6 +1348,8 @@ number of entries that can be stored.
 
   Defaults to 0.5, which will halve the size of all caches.
 
+  Note that changing this value also affects the HTTP connection pool.
+
 * `per_cache_factors`: A dictionary of cache name to cache factor for that individual
    cache. Overrides the global cache factor for a given cache.