Transaction log not releasing the unused space while shrinking

HI All,

I am trying shrink a log file.

DDCC sqpperf(logspace) - showing below results

Databasename  Logsize(MB)  Logspaceused(%)

ABCD                  301183.9      1.811704

However i took a log backup and tried to shrink the log file\

use ABCD

go

dbcc shrinkfile('ABCD_log',10)

after shrink

again i executed DDCC sqpperf(logspace) - but it was showing the result as earlier

Databasename  Logsize(MB)  Logspaceused(%)

ABCD                  301183.9      1.811704

Please let me, how to trouble shoot further?

Thanks

K