Updating benefit plan and controlling "Latest Change to Amounts" field

SOLVED

Hi all-

I need to update premiums for several benefit plans and would like for the "Latest change to amounts" field to show 3/1/2020 for all active employees with those plans.  I have experimented in our test system at making the change in "Benefit Insurance Plans" and putting the highlighted field below as 3/1/2020.  But when I save this, and even after running an update benefits process, this date is not populated into each record.  Can anyone let me now what I'm doing wrong please?