javascript:gs.hoursago(24) is Giving Me Unexpected Results

I'm testing a query of expected_start<=javascript:gs.hoursago(500) on the sysapproval_approver list.  (500 is just a number of hours for test purposes only)

500 hours ago is like back in March.  So why is it bringing back records with an expected start date of 4/3/2018?

4/3/2018 is not less than a date back in March (ie 3/1/2018) correct? 

Lisa