Daniel, more details are helpful.
If I understand your design correctly, you have the actual date as the column name? If so, this is not good design practice and you would not be able to create a reasonable chart in this manner.
Instead, you would want to create a table/sheet that has the columns Date and Attendance. Then each row is the date value and it attendance number. A visual is like this:
Date Attendance
5/1/2019 2
5/2/2019 5
5/3/2019 6
5/4/2019 4
With this table pulled into AppSheet, you would mark the Date column as the Label column. Doing so makes the charts use Date for the X axis values and you will have each date value listed along this axis. It should then be relatively easy to see how to set Attendance for the chart data points depending on which chart you desire.
I hope this helps!
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