- Examines each item's historic value for the defined field over the defined date range
- plots a line for each item
Based on the screenshots, your query is returning a list of Change Requests and plot the historic change of "Change Request Count" field on each of these items. (Likely, "Change Request Count" isn't even visible on the "Change Request" type.
Likely, "Change Request Count" is visible on a parent item type. (Maybe Project?) So you want your query to return those parent items instead. The trend chart isn't going to group or sum the item results, (The "Change Request Count" field is doing the math - the trend chart is simply plotting the changes of those values (deltas) over time - which have been saved to history in the database). For the graph to show a single line, your query should return a single item & have a single field defined in the Item Field Values: section of the chart. (If your intention is to plot by project, your query could return multiple items and then the project filter could narrow it down to single results)