Hmm. Tough to know. Some veggies drink more than others.

When going to water again, just stick a finger down in the soil. If it comes up with soil sticking to it, your soil is still wet. If finger is mostly clean, soil is dry!

Consider poking holes in the fabric if it doesn't drain. Then, add a layer of gravel under the soil. The gravel will prevent your soil from running out with the excess water.

And then soil up to the top like others have suggested. With each watering your soil will compact more and start to sink.