zfs quota question

[lhmwzy]

I create a zfs volume pool/lhm and give it quota 1M use "zfs set
quota=1m pool/lhm"

#zfs get all pool/lhm
zfs get all pool/lhm
[ttyp0][5:22:12pm]
NAME      PROPERTY       VALUE                  SOURCE
pool/lhm  type           filesystem             -
pool/lhm  creation       Tue Oct  7 17:14 2008  -
pool/lhm  used           1.00M                  -
pool/lhm  available      0                      -
pool/lhm  referenced     1.00M                  -
pool/lhm  compressratio  7.25x                  -
pool/lhm  mounted        yes                    -
pool/lhm  quota          1M                     local
pool/lhm  reservation    none                   default
pool/lhm  recordsize     128K                   default

But I cp 10 files,per file size is 2.4M to pool/lhm
#ll -h /pool/lhm
total 1013
-rw-------  1 root  wheel   2.4M Oct  7 17:18 d
-rw-------  1 root  wheel   2.4M Oct  7 17:19 dd
-rw-------  1 root  wheel   2.4M Oct  7 17:19 ddd
-rw-------  1 root  wheel   2.4M Oct  7 17:19 dddd
-rw-------  1 root  wheel   2.4M Oct  7 17:19 ddddd
-rw-------  1 root  wheel   2.4M Oct  7 17:19 dddddd
-rw-------  1 root  wheel   2.4M Oct  7 17:19 dddddd2
-rw-------  1 root  wheel   2.4M Oct  7 17:19 dddddd24
-rw-------  1 root  wheel   2.1M Oct  7 17:19 dddddd247
-rw-------  1 root  wheel   2.4M Oct  7 17:18 kldstat.core

#du -hs /pool/lhm
1.0M	.

I am puzzled,the what's zfs quota mean?
I understand is file quota,that can't put files which total size larger than 1M.
But it seems my understanding is wrong.
Anybody give a idea?