Principle
The air in the flask is a gaseous body that occupies a certain volume. So where there is air, there cannot be water at the same time. In order to fill the Erlenmeyer flask with water, the air must be displaced.
In the first part of the experiment, the air cannot flow out of the flask because the only opening is blocked by the water pressing from above. Only a few drops of water enter the flask because the air inside is somewhat compressed. The rest of the water remains in the funnel. In the second part of the experiment, on the other hand, another opening allows the air to flow out, which is observed in the beaker.