By default, when you enter 10:00 into a 4D View cell, tabbing out of the cell will display it as 10:00:00. In order to display characters as you typed, you will need to enable the forced text option.

-Go to "Style" menu and select the "Style Sheets" menu item.
-Go to the format tab and check "Forced text(data are treated as text)".
-Press OK.

Try entering 10:00 into a cell, it should display as 10:00 and not 10:00:00.

Also you can set this property programmatically.

PV SET STYLE PROPERTY (area;style; pv style format forced text; pv value on)