GPO for Windows logs

Hello,

I would like to create a group policy which does the following on Security log within windows:

Keep the log file for 30 days
Have the maximum security log size big enough to gather 30 days worth of days.

I went into GPO and set the following:

Computer Configuration-> Windows Settings->Security Settings->Event Log

Maximum security Log size:  2999936 kilobytes
Retain Security Log:  30 days
Retention method for security log: By days

I have this GPO applied to the servers that I would like to have this policy and the security logs do not exceed 32 Meg. I get an error that the security log is full when I log on.

I can manually set this, but I would like this to work with GPO's.

Can anyone shed light as to why this is not working?

Thanks in advance,

Mark