Hi, edit js/main.js in the theme folder and find line : 521

		var itemPerRow = 4;
		var containerW = $container.width();
		var items = $container.children('.hentry');
		var columns, columnWidth;
		var viewports = [ {
				width : 1300,
				columns : itemPerRow
			}, {
				width : 900,
				columns : itemPerRow-1
			}, {
				width : 480,
				columns : itemPerRow - 2
			}, { 
				width : 0,
				columns : itemPerRow - 3
			} ];

you can edit columns here.