Recently my project schedule started displaying the wrong total slack number. In the screenshot below it should display -47 not -33. I am using the same calendar throughout the project. Please advise!

Recently my project schedule started displaying the wrong total slack number. In the screenshot below it should display -47 not -33. I am using the same calendar throughout the project. Please advise!
Links:
[1] http://www.planningplanet.com/forums/microsoft-project