tikv: fix the description of in-memory-engine.capacity (#22647)

Author: hfxsd

releases/release-8.5.0.md

@@ -236,7 +236,7 @@ Compared with the previous LTS 8.1.0, 8.5.0 includes new features, improvements,
 | -------- | -------- | -------- | -------- |
 | TiDB | [`deprecate-integer-display-length`](/tidb-configuration-file.md#deprecate-integer-display-length) | Modified | Starting from v8.5.0, the integer display width feature is deprecated. The default value of this configuration item is changed from `false` to `true`. |
 | TiKV | [`raft-client-queue-size`](/tikv-configuration-file.md#raft-client-queue-size) | Modified | Changes the default value from `8192` to `16384`. |
-| TiKV | [`in-memory-engine.capacity`](/tikv-configuration-file.md#capacity-new-in-v850) | Newly added | Controls the maximum memory size that the TiKV MVCC in-memory engine can use. The default value is 10% of the system memory. The maximum value is 5 GiB.|
+| TiKV | [`in-memory-engine.capacity`](/tikv-configuration-file.md#capacity-new-in-v850) | Newly added | Controls the maximum memory size that the TiKV MVCC in-memory engine can use. The default value is `min(the system memory * 10%, 5 GiB)`.|
 | TiKV | [`in-memory-engine.enable`](/tikv-configuration-file.md#enable-new-in-v850) | Newly added | Controls whether to enable the TiKV MVCC in-memory engine to accelerate multi-version queries. The default value is `false`, which means that the in-memory engine is disabled. |
 | TiKV | [`in-memory-engine.gc-run-interval`](/tikv-configuration-file.md#gc-run-interval-new-in-v850) | Newly added | Controls the time interval at which the in-memory engine performs garbage collection (GC) on cached MVCC versions. The default value is `"3m"`.|
 | TiKV | [`in-memory-engine.mvcc-amplification-threshold`](/tikv-configuration-file.md#mvcc-amplification-threshold-new-in-v850) | Newly added | Controls the threshold for MVCC read amplification when the in-memory engine selects and loads Regions. The default value is `10`, indicating that if reading a single row in a Region requires processing more than 10 MVCC versions, this Region might be loaded into the in-memory engine.|

tikv-in-memory-engine.md

@@ -42,7 +42,7 @@ To enable the TiKV MVCC in-memory engine (IME), you need to adjust the [TiKV con
 enable = false
 
 # This parameter controls the memory size available to the in-memory engine.
-# The default value is 10% of the system memory, and the maximum value is 5 GiB.
+# The default value is `min(the system memory * 10%, 5 GiB)`. You can manually adjust the configuration to use more memory.
 # You can manually adjust this configuration to allocate more memory.
 # Note: When the in-memory engine is enabled, block-cache.capacity automatically decreases by 10%.
 capacity = "5GiB"