Sadly, they made the mem allocation with arguments now, so you need to make a new batch file (run.bat) from notepad, and type in
java -jar OSBot.jar 1255
and save it as 'run.bat' and then it will turn into a runnable file, and just double click it, make sure the osbot.jar is same name as your one
i will speak to the devs to ask them to put it back