I think the standard box of 30-30 ammunition is 20 rounds. If he was given a full box, that would have left him 12-13 rounds. Of course, he could have shot them up in practice before his jihad. Or he may have had more bullets in his pockets.
I don’t think the Mounties have said how many shots he fired inside the Parliament building.
Or how many rounds remained in the rifle or how many rounds he had on him?