I believe the wording is a bit counter intuitive because it implies, at least to me, that it is by default ("leave it") unchecked.
--- doc/source/en/TortoiseSVN/tsvn_dug/dug_settings_logcache.xml (revision 29091)
+++ doc/source/en/TortoiseSVN/tsvn_dug/dug_settings_logcache.xml (working copy)
@@ -43,7 +43,7 @@
the same URL for all repositories. Older versions of
<literal>svnbridge</literal> would do this. If you need to
access such repositories you will have to check this option.
- If you don't, leave it unchecked to improve performance.
+ If you don't, uncheck it to improve performance.
@@ -57,7 +57,7 @@
reasons this is a bad idea - a UUID should be
<emphasis>unique</emphasis>. However, the log cache will
still work in this situation if you check this box.
- If you don't need it, leave it unchecked to improve performance.
+ If you don't need it, uncheck it to improve performance.