Shell Programming and Scripting

Hello everyone,
I would like to filter and search for files in my curr dir where the blocks used by those files are over a certain number (i.e. 30), when I try this command

find . -name "c*" -size +30 -exec ls -ls {} \;

I get a list of files, the first column is the block size, right?

368 -rw-rw-r-- 1 xxx staff 374426 Dec 02 13:26 ./test_in
20 -rw-rw-r-- 1 xxx staff 19554 Dec 01 10:49 ./testout

Why is a file using 20 blocks getting listed there?
I hope you can shed some light on this.
Thanks.

find uses a block size of 512.

From manual:

-size n[c] True if the file is n blocks long (512 bytes
per block). If n is followed by a c, the
size is in bytes.

apparantly, ls -s uses a block size of 1024.