diff --git a/docs/en/config/log.md b/docs/en/config/log.md
index 04722f2c..8c1b43d2 100644
--- a/docs/en/config/log.md
+++ b/docs/en/config/log.md
@@ -55,3 +55,5 @@ Currently, the available levels are `quarter`, `half`, and `full`. The masking f
 
 - ipv4 `1.2.*.*` `1.*.*.*` `[Masked IPv4]`
 - ipv6 `1234:5678::/32` `1234::/16` `[Masked IPv6]`
+
+For more specific requirements, you can use a custom format such as `/16+/32`. The format defines the number of bits to keep unmasked; the first number is for IPv4 and the second for IPv6. Note that the IPv4 value must be divisible by 8. Using /32 (IPv4) or /128 (IPv6) means no masking, while /0 will display as `[Masked IPv4/IPv6]`.