why after subtraction extra spacing generating in batch script

I AM trying to copy my dbf file into backup folder according to every Monday,if the Monday is not greater then 7 then it will copy previous month file .but when i subtract the month by one it taking extra space

cls @echo off

for /F "tokens=1-4 delims=/ " %%i in ('date /t') do ( set WD=%%i set D=%%j set M=%%k set Y=%%l )

set day="SUN" set now="%WD%" set /a ss=%M%-1

set j=0%ss%

IF /I "%now%"=="%day%" ( set month=%M% ) ELSE ( IF %D% LEQ 7 ( set month=%j% ) ELSE ( set month=%M% ) )

echo S2?%month%160.dbf

OUTPUT: S2?03 160.dbf

I NEED LIKE S2?03160.dbf

CAN ANY ONE HELP ME....