Why am I getting "ECHO is off."?

Question

I recently wrote the code below on a batch file:

@echo off
cls
chcp 65001 >nul

for /f "Delims=" %%j in (%cd%\poo.txt) do (
   echo %%j
   set /a lo=%%j+1
   echo %lo%
   pause
)

The file appropriately titled "poo.txt" contains a number, '0' in this case. When the code is ran, it displays this output:

0
ECHO is off.
Press any key to continue...

Everything seems to have worked, except for when the code is supposed to show 0 + 1. Instead, it outputs "ECHO is off." I don't really get this error. I've been trying to find some kind of typo or mistake in my code, but I don't see anything wrong to my knowledge.

Answer 1

Back to share that the issue is that this simple line:

echo %lo%

Should be replaced with,

echo !lo!

Anyway, goodbye.