License tab in windows media player

Hello all,
Once i play a file with right set in license for unlimited play , all the
other files which have the rights set as 30 days play also show unlimited
number of play right under the File-> Properties->license tab of windows
media player 10.
Why does this happen?
Although the file does expire after 30 days, but why does it show unlimited
play under the license tab?
Thank you.