I *think* the bigger numbers are harder pressure, but am not 100% sure just from memory. Try it and see, it should be pretty obvious, probably even to just pokin' it with a finger as opposed to actually trying to run a scrap of fabric thru it.
Usually you'd use lighter pressure with thicker fabrics (especially thick puffy things like polarfleece).
Actually I don't find myself adjusting it on my own machine hardly ever, since I switched to using a roller foot all the time instead of the usual kind. (That's probably why I don't remember for certain which direction the numbers go). I reeeeeeallly like my roller foot. The only slight disadvantage is that it is not split in front like a conventional foot.
And you also know about the lever to disengage the feed-dogs, for if you want to do freehand quilting or if you are working on a particularly thick/cumbersome/awkward bit such as where several seams cross, yes? The lever is usually underneath the throat plate of the macine, you only see it when you have the compartment open to change the bobbin. I know you probably know this, just mentioning it in case