Point the cleanup commands at the previous mark

Author: lixmal

src/pages/client/environment-variables.mdx

@@ -43,11 +43,12 @@ Container network plugins, CNIs and other VPNs claim bits of the mark space for
 The client removes the routing rule for its mark range on shutdown. If you change `NB_FWMARK_BASE` while the client was not shut down gracefully (killed, crashed, host reset), the rule for the previous range stays behind and has to be removed by hand, otherwise traffic keeps being sent to the NetBird routing table:
 
 ```shell
-# Find the leftover rule, it names the old mark
+# Find the leftover rule, it names the mark of the previous range
 ip rule show
 ip -6 rule show
 
-# Remove it, for both families
+# Remove it for both families, with the mark the rules above named
+# (0x1bd00 here is the default base, use the previous one if it was custom)
 sudo ip -4 rule del not from all fwmark 0x1bd00 lookup netbird priority 110
 sudo ip -6 rule del not from all fwmark 0x1bd00 lookup netbird priority 110
 ```