diff --git a/usr.sbin/quot/quot.8 b/usr.sbin/quot/quot.8
--- a/usr.sbin/quot/quot.8
+++ b/usr.sbin/quot/quot.8
@@ -41,7 +41,9 @@
 The
 .Nm
 utility
-is used to gather statistics about the disk usage for each local user.
+is used to gather per-user disk usage statistics from
+.Xr ffs 7
+file systems.
 .Pp
 The following options are available:
 .Bl -tag -width indent
@@ -51,8 +53,16 @@
 Display three columns containing number of blocks per file,
 number of files in this category, and aggregate total of
 blocks in files with this or lower size.
+This option is mutually exclusive with the
+.Fl n
+option.
 .It Fl f
 For each user, display count of files and space occupied.
+This option has no effect if combined with the
+.Fl c
+or
+.Fl n
+options.
 .It Fl k
 Force the numbers to be reported in kilobyte counts.
 By default, all sizes are reported in 512-byte block counts.
@@ -69,9 +79,17 @@
 .Ed
 .Pp
 to get a report of files and their owners.
+This option is mutually exclusive with the
+.Fl c
+option.
 .It Fl v
 In addition to the default output, display the number of files
 not accessed within 30, 60 and 90 days.
+This option has no effect if combined with the
+.Fl c
+or
+.Fl n
+options.
 .El
 .Sh ENVIRONMENT
 .Bl -tag -width BLOCKSIZE
@@ -88,6 +106,7 @@
 .Xr quota 1 ,
 .Xr getmntinfo 3 ,
 .Xr fstab 5 ,
+.Xr ffs 7 ,
 .Xr mount 8
 .Sh HISTORY
 This implementation of