Hi Dave, thanks for your comment! Breww allows you to rack the full volume of the container you are racking into when racking off another container. You cannot part-fill a container when racking off of another container; therefore, in your scenario, a 30L container wouldn’t appear, as you cannot rack the full volume, as you only have 20L. If you would like to part-fill containers when racking from another container, it would be great if you could raise this as a feature request, Cheers!