Field scale (decimal places) issuse

I noticed that when using arcpy.CalculateField_management in python on a feature class it's changes the field scale (decimal places).
I had a shapefile with an Acres filed of field scale of 3 but now it seems to have a field scale of 11. Why after running arcpy.CalculateField_management does it change the field scale? This is annoying after your export the table and open it.

Any explanation or help would be great.

Thanks.