First, head to your Project List.
Next, click "Edit Custom Columns" on the far right to add and sort your Custom Columns

After, click 'Sales'.
Then, add the Custom Column for 'Product Subtotal (Signed)'

Click Update Columns once you have the columns you'd like.

Finally, apply any filters you need (such as sale lead, dates, or venue),

Then, you'll be able to hover over the column header and you'll see a total of that column.