Trans Log-&>space Allocated 27GB, Space Used 100MB

Hi.. I was doing a good maintenance on my DB and my trans log LDF keep growing until 30GB but my DB data file MDF is only 2GB. I found the two following method to reduce my log size.

Method 1: I used veritas to backup log file with truncate
Method 2: I used the shrink database option in Enterprises manager to shrink it (file chosen=log , use default option)

After doing that, I found my LDF log file is still about the same size=27GB but when I see clearly, from the shrink database windows, the log spaced used reduced to only 100MB, the allocation log space is still 27GB. Why? How to make the LDF smaller to be the around the same size as the space used 100MB?