This is the output I get:

Warning: Output file "D:\Video\MKVConvert\Test1 - Cop#!¤$y - Copy.mkv" already exists. Skipping...

Warning: Output file "D:\Video\MKVConvert\Test1 - Copy.mkv" already exists. Skipping...

Processing: "Test1.mkv"
mkvmerge v86.0 ('Winter') 64-bit
'D:\Video\Test1.mkv': Using the demultiplexer for the format 'Matroska'.
'D:\Video\Test1.mkv' track 0: Using the output module for the format 'AVC/H.264'.
'D:\Video\Test1.mkv' track 1: Using the output module for the format 'AC-3'.
'D:\Video\Test1.mkv' track 2: Using the output module for the format 'text subtitles'.
The file 'D:\Video\MKVConvert\Test1.mkv' has been opened for writing.
The cue entries (the index) are being written...
Multiplexing took 10 seconds.
Successfully processed "Test1.mkv"

All MKV files have been processed and saved in "D:\Video\MKVConvert".
Press any key to continue . . .

When running this script:

@echo off

REM ===========================
REM Configuration
REM ===========================

REM Destination directory where processed files will be saved
set "DEST_DIR=D:\Video\MKVConvert"

REM Path to the mkvmerge executable
set "MKVMERGE=C:\Program Files\MKVToolNix\mkvmerge.exe"

REM ===========================
REM Setup
REM ===========================

REM Create destination directory if it does not already exist
if not exist "%DEST_DIR%" (
    echo Creating destination directory: "%DEST_DIR%"
    mkdir "%DEST_DIR%"
    if errorlevel 1 (
        echo Error: Failed to create destination directory.
        echo Please check permissions or the path and try again.
        echo.
        pause
        exit /b 1
    )
)

REM Check if mkvmerge exists
if not exist "%MKVMERGE%" (
    echo Error: mkvmerge executable not found at "%MKVMERGE%".
    echo Please verify the path to mkvmerge.exe.
    echo.
    pause
    exit /b 1
)

REM ===========================
REM Processing
REM ===========================

REM Loop through each MKV file in the current directory
for %%a in (*.mkv) do (

    REM Check if the output file already exists
    if exist "%DEST_DIR%\%%~nxa" (
        echo Warning: Output file "%DEST_DIR%\%%~nxa" already exists. Skipping...
		echo.
    ) else (
        REM Display a message indicating processing
        echo Processing: "%%~nxa"

        REM Execute mkvmerge to process the file
        "%MKVMERGE%" ^
            --ui-language en ^
            --priority highest ^
            --video-tracks 0 ^
            --audio-tracks 1 ^
            --subtitle-tracks 2 ^
            --no-attachments ^
            --no-global-tags ^
            --no-track-tags ^
            --no-chapters ^
            --language 0:en ^
            --track-name 0: ^
            --default-track-flag 0:yes ^
            --language 1:en ^
            --track-name 1: ^
            --default-track-flag 1:yes ^
            --sub-charset 2:UTF-8 ^
            --language 2:en ^
            --track-name 2: ^
            --default-track-flag 2:yes ^
            --title "" ^
            --track-order 0:0,0:1,0:2 ^
            --output "%DEST_DIR%\%%~nxa" ^
            "%%~fa"

        REM Check if the processing was successful
        if errorlevel 1 (
            echo Error: Failed to process "%%~nxa". Please check the input file and try again.
			echo.
        ) else (
            echo Successfully processed "%%~nxa"
			echo.
        )
    )
)

REM ===========================
REM Completion Message
REM ===========================

REM Display a completion message for processing
echo All MKV files have been processed and saved in "%DEST_DIR%".

REM Pause the script to allow the user to see the output
pause

Instead of saying "All MKV files have been processed and saved in "D:\Video\MKVConvert"." when either only processing none, one or twenty files, how can I make it count how many files it processes, and if it processes none, then say that?