there should be a separate help screen.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@20987 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/resources/hudson/security/ProjectMatrixAuthorizationStrategy/help.html

+<div>
+    This mode is an extension to "Matrix-based security" that allows additional ACL matrix to be defined
+    for each project separately (which is done on the job configuration screen.)
+
+    <p>
+    This allows you to say things like "Joe can access project A, B, and C but he can't see D."
+    See the help of "Matrix-based security" for the concept of matrix-based security in general.
+
+    <p>
+    ACLs are additive, so the access rights granted below will be effective for all the projects.
+</div>