Issue:
Explains why previous records still exist in the Activity table after you marked the Clear Stranded Activity Records check box on the Timeout tab.
More Information:
After the Inactivity Timeout process runs, it will clear anything that has a date before the system date minus 2 hours minus the length of the timeout limit. For example, if your timeout limit is 60, then it will clear any ACTIVITY records that are at least 3 hours old. So, records from a few days ago should get cleared out.
If those records are not being cleared out, then it is possible that the Inactivity Timeout process never ran.
A user must be logged in to GP in order for the process to start in the first place. If you logged out of GP a few days ago, came back and looked in the Activity table a few days later, but you never logged into GP and stayed in long enough for the process to run, then the records will still be there.