I think I know what the problem is. A dual value can only have one possible text representation for a numerical value. The real value of the dual is the numeric - the text is only the display representation of the value.
I expect that you have a POLICY_PERIOD value somewhere else for POL_PERIOD_FROM = 31 March (Mar-16 - Mar-27). In the model, the dual will be stored as a numeric with a single display format. So the display value for 31 March 2016 is the value in POLICY_PERIOD.
If you want to correctly reflect you would have to create a numeric value that considers both the _FROM and _TO fields. You could try this if you want to return a valid date value that reflects the FROM date: