Can the user_session_length be set to a fractional number, i.e. 0.5 for a half day?

I ask because I am trying to set it to 0.04167 which equates to about 1 hour, yet the session seems to expire long before that.

I am using the value from this setting to implement a javascript auto-logout warning and subsequent auto-logout feature. Basically 5 minutes before the user's session expires, I alert them that their session is ABOUT to expire. They can choose to 'Resume' or 'Logout'. If they do not make a choice within 1 minute, I auto-dismiss the dialog and proceed to log them out. If they 'Resume', I reset the session_date in Sessions table and start over, thus extending their session.

It is 99.99% completed/working. I'm just left ironing out the actual timing details which is why I need to know if I can use a decimal number for user_session_length. The user_session_length setting accepts the decimal fraction, and I am able to calculate my values from the setting, but I seem to be logged out (session expired) very quickly.

Thanks for any assistance. I'll post the code if anyone is interested.
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