Per the directions, you want to plant ~10 seeds in your Garden-In-A-Can. If they all successfully germinate and sprout, that will be too many little basil or cilantro plants competing for space. Ideally you will have 1-3 plants growing in each can.
If you find you have more than 1-3 seedlings, you can thin them out to ensure the remaining plants flourish. Here is a great article on how to do so.
Also, light is key for growing herbs and greens. During the darker fall and winter months you'll boost plant growth by 1000x by having a grow bulb like this!
If you have any additional questions about growing your garden, don't hesitate to ask!