Change how long a computer is out of date before it lists in SEC.

So, I've tried doing searches but nothing is showing up. I've noticed that quite often computers will show up in the Out-Of-Date list yet show "Not Since" about 2 hours ago. That seems a bit sensitive to me. Is there a way to change it so that a computer has to be out of date for 24-48 hours before it shows up? 

Thanks.