There is no limit to the amount of Colloidal Silver you can make at one time other than the size of your container and how long you want to wait for it.
Typically, people make anywhere from a few ounces to as much as a gallon or more at a time. Naturally, a gallon will take considerably longer than a couple of ounces, but the length of time is the only real difference.
One VERY IMPORTANT fact: the length of time involved is totally based on the QUALITY and the AMOUNT of water being used. The more water you use and the purer the water the longer it will take.
Remember, the finished product should be clear to a slightly yellow tint. If there is any cloudiness or milky look to it, the distilled water being used has too many impurities in it.