Chart element-Group by: How to set grouping

Hello Bubbler! I’d like to create a line chart using Chart Element Plugin to show the transition of the number of registered users per day.
But I can’t set up Grouping in Data source, can you please advise?

I’d like to create a chart that shows the number of registrants on the vertical axis and the creation date on the horizontal axis.

The current Data source settings and chart preview looks like below.


Thanks in advance.