Batch file error "/100 was unexpected at this time"

I make a game for fun with batch script but in this code i have an error message "/100 unexpected at this time" i really don't understand why? Please help me!!

@echo off
mode con cols=110 lines=32
setlocal enabledelayedexpansion

set npctier=0
goto randomnpc

:randomnpc
if %npctier% EQU 0 ( 
set npctype=Wooden Dummy
set /a npclvl=%random% %% 5+1
set /a npchp=%npclvl% * 100
set /a npcdmg=0
set /a npcdef=(%npchp%*5)/100
set /a npcxp=%npclvl%*100 )

:combatchoice
echo.
echo. You see %npctype% level %npclvl%.
echo.
echo. The %npctype%'s Health: %npchp% HP
echo.
goto main