Can't set Auto-logout settings

I’m setting the Auto-logout behavior to not log out the user after a set period. This is usually found in System Preferences -> Security & Privacy -> Advanced; we’re setting it via a script. For most of our users, the script passes the parameter 3600 (60 minutes); for devs, like this user, we set it 0. Here’s the script:

#!/bin/sh
# this script controls the auto logout delay
# AutoLogOutDelay=0 is disabled, all other values enable
# logoutvalue is number of seconds until user is logged out
# parameters
logoutDelay=$4
defaults write /Library/Preferences/.GlobalPreferences com.apple.autologout.AutoLogOutDelay  -int $logoutDelay
defaults write /Library/Preferences/.GlobalPreferences com.apple.securitypref.logoutvalue -int $logoutDelay

We can use defaults read… to verify that JAMF is successfully setting his machine’s values to 0. Yet when we look at the state of the System Prefs pane, it shows 30 minutes! After viewing the GUI, defaults read… reveals that the values have been reset to 1800.

I’m stumped as to why/how it keeps getting reset and where the 1800 value is coming from.