Your Your "Year/Month" formula {@Year}&"/"&{@Month Format}
IS producing a string output. When you use & to concatenate a number, it automatically formats it to have two decimal places.
Try Totext({@Year},0,"")+"/"+Totext({@Month Format},0,"")
the ,0,"" part of the totext function tells crystal to convert the number {@Year} and {@Month Format} to a string but put 0 decimal places and use "" (empty string) as the thousands separator.