the rules of find -cmin 0 and -ctime 0

Question

I was studying the command find, and I saw:

-cmin n
              File's status was last changed n minutes ago.
-ctime n
              File's status was last changed n*24 hours ago.

but when n is zero, comes the difference, is there a sound explanation for this behavior?

$ date
Thu 23 Jul 2020 02:16:17 PM CST
$ 
$ touch a 
$ find -name a -cmin 0
$ find -name a -cmin 1
./a
$ find -name a -ctime 0
./a
$ find -name a -ctime 1
$ 
$ date
Thu 23 Jul 2020 02:16:18 PM CST
$