My advice is a little gray and will require you to be a bit careful. But consider adding whatever you are good at or whatever is relevant to the role you are applying for to that time period.
For instance, if you are comfortable with some technology or framework etc but have never used it formally at work, you can include that. If you have done some side projects, feel free to include them here.
Point being, no body goes and checks what you did at that company. They do check the dates you worked at a company and your behaviour etc, but never exactly what you did.
The interviewer will ask you for more details on what you did at that job, what challenges you faced, etc. And why you quit that job if it's recent. As long as you answer that well, you are good to go.