diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 8efad57766..d134ec798a 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -939,13 +939,17 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPoolType|0x0|UINT64|0x30001053
 
   ## This mask is to control Heap Guard behavior.
+  # Note that due to the limit of pool memory implementation and the alignment
+  # requirement of UEFI spec, BIT7 is a try-best setting which cannot guarantee
+  # that the returned pool is exactly adjacent to head guard page or tail guard
+  # page.
   #   BIT0 - Enable UEFI page guard.<BR>
   #   BIT1 - Enable UEFI pool guard.<BR>
   #   BIT2 - Enable SMM page guard.<BR>
   #   BIT3 - Enable SMM pool guard.<BR>
   #   BIT7 - The direction of Guard Page for Pool Guard.
-  #          0 - The returned pool is adjacent to the bottom guard page.<BR>
-  #          1 - The returned pool is adjacent to the top guard page.<BR>
+  #          0 - The returned pool is near the tail guard page.<BR>
+  #          1 - The returned pool is near the head guard page.<BR>
   # @Prompt The Heap Guard feature mask
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask|0x0|UINT8|0x30001054
 
diff --git a/MdeModulePkg/MdeModulePkg.uni b/MdeModulePkg/MdeModulePkg.uni
index 43dd5103be..fb45ccb768 100644
--- a/MdeModulePkg/MdeModulePkg.uni
+++ b/MdeModulePkg/MdeModulePkg.uni
@@ -1196,13 +1196,17 @@
 #string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdHeapGuardPropertyMask_PROMPT  #language en-US "The Heap Guard feature mask"
 
 #string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdHeapGuardPropertyMask_HELP    #language en-US "This mask is to control Heap Guard behavior.\n"
+                                                                                            "Note that due to the limit of pool memory implementation and the alignment\n"
+                                                                                            "requirement of UEFI spec, BIT7 is a try-best setting which cannot guarantee\n"
+                                                                                            "that the returned pool is exactly adjacent to head guard page or tail guard\n"
+                                                                                            "page.\n"
                                                                                             "   BIT0 - Enable UEFI page guard.<BR>\n"
                                                                                             "   BIT1 - Enable UEFI pool guard.<BR>\n"
                                                                                             "   BIT2 - Enable SMM page guard.<BR>\n"
                                                                                             "   BIT3 - Enable SMM pool guard.<BR>\n"
                                                                                             "   BIT7 - The direction of Guard Page for Pool Guard.\n"
-                                                                                            "          0 - The returned pool is adjacent to the bottom guard page.<BR>\n"
-                                                                                            "          1 - The returned pool is adjacent to the top guard page.<BR>"
+                                                                                            "          0 - The returned pool is near the tail guard page.<BR>\n"
+                                                                                            "          1 - The returned pool is near the head guard page.<BR>"
 
 #string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdCpuStackGuard_PROMPT  #language en-US "Enable UEFI Stack Guard"