/timer1 1 $3 .ban -ku $+ 30 $chan $2 $4-
Two things here,
The first is simply that you dont need / or // within a script. Simply put mirc always treats every command in a script as if it is //
The second thing, far more important is it is incredibly BADFORM to use a number as a timer name, doubly so to use "1" since this well overwrite the first unnamed timer in your system. name a timer anything but just a number, as there are also access problems to timers named as numbers when useing $timer(). I Suggest ....
TIMERwarner 1 $3 .ban -ku $+ 30 $chan $2 $4-