With comments from dear Yna D. again, it's verified that the behavior was caused by the length unit is millimeter but area square meters and volume cubic meters. Changing the length unit to meter or making the Length value bigger such as 5000 mm would make the behavior return to normal.
We did not notice that because the Revit Global Parameters dialog does not display unit for length values though do so for area and volume ones.
In fact, the Global Parameter Editor tool of Revit Parameter Organizer displays unit for length parameters as well. It was clearly displayed as mm there, thus those area and volume values should be really zero as their decimal digits only had two or three. We should have noticed that early. Sorry about it. Maybe we were too busy around that moment with improving and testing new builds of Revit Parameter Organizer 2019.