Windows batch: Delete files older then N, but left last M files

Question

I am trying get this batch, but can't find looking good solution:

@echo off
setlocal enableextensions enabledelayedexpansion

set Folder=C:\DeployArchive\demo
set /a "Count=20"

mkdir %Folder%\tmp
for /f "skip=%Count% usebackq delims=" %%i in (
    `dir /b /a:-d /o:-d /t:w "%Folder%"`
) do move %Folder%\%%~i %Folder%\tmp\%%~i"

forfiles /p %Folder%\tmp /s /d -30 /c "cmd /c del /s /f @file /q"

move /y %Folder%\tmp\* %Folder%\

rmdir %Folder%\tmp

I was made it to work, but as you see it's massive. Can someone may help me?