SAS numeric formats round - the CEIL, FLOOR and ROUND functions can influence this behavior with pre-processing in a DATA step, otherwise you can display the value as formatted with your own defined PROC FORMAT (using PICTURE). A link to a SAS conference paper is provided below, as well as having SAS-hosted documentation at the SAS support http://support.sas.com/ website and other technical papers available using the SEARCH facility.
To demonstarte data with more decimal places than monber, suppose we create data like bmi on sashelp.class
As I don't know the unit conversion, the following is just approximately "logical"
[pre]data classb ;
set sashelp.class ;
myBMI = height**3 / weight ;
proc format ;
picture truncat .=. other = '00001.23'(mult=100) ;
proc tabulate ;
class age ;
var myBMI ;
table ( all age all ), n*f=3. mybmi*(mean='trunc'*f=truncat.
run ; [/pre]It is tested in SAS9.2 but would probably run in SAS6
run that and see if it demonstrates the truncation required
There is an option for numeric user formats to round before formatting. That feature is not used in my example, above.