Changing filled contour label decimal places

[fred7]

Hello,
I interpolated water parameters from CSV file and got the filled contours. I would like to add the contour color values as legend in layout view, but there are too many decimal places. In Symbology -> "Classify" there is no "Advanced" button to change the label decimal places. Is there any possibility to change the Label decimal places or do I have to do it manually (under Symbology->Classify->Label)? I attached informative picture.

[RobertBorchert]

Are your contour elevations are not stored as an Integer (long or short)?

[fred7]

If I import the CSV file from Menu -> Map -> Add Data -> XY Point Data, and look at the Attribute Table, all values (temperature, salinity etc) are declared as Type:DOUBLE.

After I have imported the CSV file then I use Geostatistical Wizard to interpolate water surface values using Kernel Interpolation (with barriers).