Custom Sensor - bash script

I installd cygwin to use bash scripts on the Windows machine, where i testing PRTG.

For a custom sensor i made a batch file called bash.bat

@echo off
FOR /F "tokens=*" %%a in ('c:\cygwin64\bin\bash.exe -c "/usr/local/bin/%1 %2') do SET OUTPUT=%%a
echo %OUTPUT%

The first argument is the name of the bash script located in c:\cygwin64\usr\local\bin\ The second argument can be a IP address

My first script "brother-toner.sh" use snmpwalk to collect information from a brother printer and calculate the toner level

#!/bin/bash
FULL=`snmpwalk -v1 -c public $1 ..some oid path...`
LEFT=`snmpwalk -v1 -c public $1 ..some oid path...`
LEVEL=$((${FULL: -1}*100/${LEFT: -1}))
OUTPUT="${LEVEL}:Black"
echo $OUTPUT

if i run "bash.bat 192.168.0.1" from terminal i get something like
66:Black

But PRTG don't get the value (66)

If i set the value e.g in bash script (OUTPUT="66:Black") or in bat file (echo 66:Black) it works.

Strange but also works: "echo 10%OUTPUT%" -> value in PRTG is 10

Encoding missmatch?

bash cygwin script