@echo off
setlocal enableextensions enabledelayedexpansion

set sFolder="C:\Users\user\Documents\ZVIT_ARC"
set /a iCount = 15

for /f "skip=%iCount% usebackq delims=" %%i in (
	`dir /b /a:-d /o:-d /t:w "%sFolder%"`
) do del /f /q "%sFolder%\%%~i"

endlocal
exit /b 0