Change default value and use more sane examples

Mention also increasing request size is not possible, it can only reduce
the accepted size.

Resolves coredns#295

Signed-off-by: Petr Menšík <pemensik@redhat.com>

content/plugins/bufsize.md

@@ -8,24 +8,25 @@ date = "2022-05-10T17:23:57.8775785"
 +++
 
 ## Description
-*bufsize* limits a requester's UDP payload size.
+*bufsize* reduces a requester's UDP payload size.
 It prevents IP fragmentation, mitigating certain DNS vulnerabilities.
-This will only affect queries that have an OPT RR.
+It cannot increase UDP size requested by the client, it can be reduced only.
+This will only affect queries that have an OPT RR (EDNS(0)).
 
 ## Syntax
 ```txt
 bufsize [SIZE]
 ```
 
 **[SIZE]** is an int value for setting the buffer size.
-The default value is 512, and the value must be within 512 - 4096.
+The default value is 1232, and the value must be within 512 - 4096.
 Only one argument is acceptable, and it covers both IPv4 and IPv6.
 
 ## Examples
 Enable limiting the buffer size of outgoing query to the resolver (172.31.0.10):
 ```corefile
 . {
-    bufsize 512
+    bufsize 1100
     forward . 172.31.0.10
     log
 }
@@ -34,7 +35,7 @@ Enable limiting the buffer size of outgoing query to the resolver (172.31.0.10):
 Enable limiting the buffer size as an authoritative nameserver:
 ```corefile
 . {
-    bufsize 512
+    bufsize 1220
     file db.example.org
     log
 }