value too great for base error token is 09

I dont know but some videos still working with this script but some is not working and have this error, i dont know how to fix it

Error
Code:/mnt/c/Users/GEN32AC/ezthumb_linux/ffsplit: line 25: let: 09: value too great for base (error token is "09")
Using default output file format : 116ABME-%03d.mp4
/mnt/c/Users/GEN32AC/ezthumb_linux/ffsplit: line 50: [: : integer expression expected

Script
Code:#!/bin/bash

# Written by Alexis Bezverkhyy <alexis@grapsus.net> in 2011
# This is free and unencumbered software released into the public domain.
# For more information, please refer to <http://unlicense.org/>

function usage {
echo "Usage : ffsplit.sh input.file chunk-duration [output-filename-format]"
echo -e "\t - input file may be any kind of file reconginzed by ffmpeg"
echo -e "\t - chunk duration must be in seconds"
echo -e "\t - output filename format must be printf-like, for example myvideo-part-%04d.avi"
echo -e "\t - if no output filename format is given, it will be computed\
automatically from input filename"
}

IN_FILE="$1"
OUT_FILE_FORMAT="$3"
typeset -i CHUNK_LEN
CHUNK_LEN="$2"

DURATION_HMS=$(ffmpeg -i "$IN_FILE" 2>&1 | grep Duration | cut -f 4 -d ' ')
DURATION_H=$(echo "$DURATION_HMS" | cut -d ':' -f 1)
DURATION_M=$(echo "$DURATION_HMS" | cut -d ':' -f 2)
DURATION_S=$(echo "$DURATION_HMS" | cut -d ':' -f 3 | cut -d '.' -f 1)
let "DURATION = ( DURATION_H * 60 + DURATION_M ) * 60 + DURATION_S"

if [ "$DURATION" = '0' ] ; then
echo "Invalid input video"
usage
exit 1
fi

if [ "$CHUNK_LEN" = "0" ] ; then
echo "Invalid chunk size"
usage
exit 2
fi

if [ -z "$OUT_FILE_FORMAT" ] ; then
FILE_EXT=$(echo "$IN_FILE" | sed 's/^.*\.\([a-zA-Z0-9]\+\)$/\1/')
FILE_NAME=$(echo "$IN_FILE" | sed 's/^\(.*\)\.[a-zA-Z0-9]\+$/\1/')
OUT_FILE_FORMAT="${FILE_NAME}-%03d.${FILE_EXT}"
echo "Using default output file format : $OUT_FILE_FORMAT"
fi

N='1'
OFFSET='0'
let 'N_FILES = DURATION / CHUNK_LEN + 1'

while [ "$OFFSET" -lt "$DURATION" ] ; do
OUT_FILE=$(printf "$OUT_FILE_FORMAT" "$N")
echo "writing $OUT_FILE ($N/$N_FILES)..."
ffmpeg -i "$IN_FILE" -vcodec copy -acodec copy -ss "$OFFSET" -t "$CHUNK_LEN" "$OUT_FILE"
let "N = N + 1"
let "OFFSET = OFFSET + CHUNK_LEN"
done