I'm using Ubuntu (16.04).
docker images gives the top line shown. Interestingly it says created 10 weeks ago when it definitely was created yesterday and didn't exist before then.
Docker ps -a gives the lines at the bottom.
No idea what the 'Names' at the end are - I don't recognize them.
The created entry is for when the image was created. While you imported it yesterday, it wasn't created yesterday.
It looks like you have 3 containers. The NAMES is usually a user-friendly name that you assign. In the case of the script that you ran, it should have named the container "sandbox". However, you can see there are 3 containers and none of them are named sandbox. That is why you are seeing the error you are seeing.
1. docker rm <container id> for each of the 3 containers
2. Trying creating the container using just the docker run command from the script the tutorial has you download. The docker run command is between the else and fi.
If the docker run command still does not properly create the container with the name sandbox, you can always start the sandbox using the container id like docker start <container id>.