You won't draw it "value-wise", since you don't have any values provided. You are going to use an arbitrary scale.
Anyway, here is the idea :
- time = 0 seconds. There is no water, height = 0.
- time = 1 second. There is a little height of water, say .
- time = 2 seconds. There is some more water, but not , because the container gets larger and larger.
- time = 3 seconds. Some more water, but it is even less than , same reason.
Maybe you could actually have fun doing this problem
If you have water and a standard glass near you, you can do the experiment. Each time, pour some water (always the same quantity of water), and record the height of the water on the graph. And see how it looks . This will help you understand even more than from a forum because you will actually know what you are doing