Note you will always have a gap, it’s not real life and this is a result of how the simulation works. If you have a couple of thousand euros spare you can get Realflow.
There are some things you can change which will help.
- Change fluid from a shell to a volume
- Make the domain smaller to just surround the container
- Change real world size to 0.1 (10cm)
- Use Ctrl+A on all objects to make sure their scale value is set to 1
In your blend the size of the container receiving the fluid is simulated to be about 3mm. Make this bigger to get a better simulation - The longest dimension of your domain is the real-world size (m) in the domain settings. Make the domain just big enough to contain where you want the fluid and the real-world size to a realistic figure.
You will still get a gap but cgi is all about faking things. The size of containers do not have to stay the same after you have baked the fluids. You have to learn to get around the inherent limitations.