You can change the value of the calculated variable to include the %-symbol, but I recommend using the format statement to change the way the value is displayed.
[pre]data td.sample;
set td.sample;
format Percentage percent10.2;
Percentage=(total/300);
run;[/pre]
Please notice the description of the format found in the SAS online documentation:
The PERCENTw.d format multiplies values by 100, formats them the same as the BESTw.d format, and adds a percent sign (%) to the end of the formatted value, while it encloses negative values in parentheses.