Hello @gtran and welcome to the SAS Support Communities!
If that constant number is contained in a variable of the input dataset (abc), you can use the WEIGHT statement to obtain the desired adjusted frequencies. Otherwise, you can add such a weight variable in a preliminary DATA step as shown below (creating a view to avoid redundancy), but for large input datasets it might be more efficient to multiply the frequencies in a subsequent DATA step using the mostly smaller output dataset (xyz) from PROC FREQ.
data _tmp / view=_tmp;
set sashelp.class;
_w=3.14;
run;
proc freq data=_tmp;
tables age*sex / out=want;
weight _w / zeros;
run;