Microsoft Gantt 3.0.12.0 Duration

I am using the custom visual, Microsoft Gantt 3.0.12.0. I have added the Task, Start Date, and Duration. My issue is with the Duration. I have a Duration field in my data set (specified in number of weeks). Because of how the data is that I received, all projects have a Start Date and Duration, but they do not all have an End Date. Because of this, I'm trying to use my Start Date field as the Start Date and my Duration field as the Duration. However, when I add my Duration field to the Duration slot in the visual, it does a "count" rather than simply use the value. Because of this, all of my projects have the correct start date, but only last a single day because it's doing a count rather than using the value. How can I get the visual to use the numerical value specified in the Duration field rather than count it?

Thanks!