Rockwell Automation Logix5000 Controllers Tasks, Programs, and Routines Programming Manual - Manual (Page 31)

Manage tasks Chapter 1
The same applies for 66% and higher, except that there are multiple 1 ms intervals.
For example, at 66% there are two 1 ms intervals of consecutive time and at 90%
there are nine 1 ms intervals of consecutive time.
Configure the system-overhead time slice
Follow these steps to configure the system-overhead time slice.
1. On the Online toolbar, click the controller properties icon.
2. On the Controller Properties dialog box, click the Advanced tab.
3. In the System Overhead Time Slice box, enter a number.
Rockwell Automation Publication 1756-PM005-EN-P - October 2014 31