Each line shows the Invoice #, the Finalize Date, the invoice's Gross Sales, the Part Sale Price After Discount (what the customer paid for the parts on that invoice), the OPP Amount (what you paid suppliers for parts bought in for the job), COG-Inventory (the cost of parts taken from your own stock), the Total parts cost, and Gross Profit % on the parts. The Total: row at the foot adds up the five money columns for the lines on the page you are looking at. It leaves Gross Profit % blank.
Gross Profit % is worked from the parts figures only. It does not use Gross Sales, even though that column sits beside it. Gross Sales includes labor and everything else on the invoice. The percentage compares the parts sale price with the parts cost.
A line showing 100.00 % usually means no cost was recorded, not that the parts were free. When an invoice's parts were not linked to an inventory item or an outside part purchase, the cost columns read $0.00 and the percentage comes out at 100 %. Treat such lines as invoices to check. Example: invoice 335230 sold $171.96 of parts with $0.00 cost recorded.
The Total: row covers only the page on screen, and there is no report-wide total anywhere on the page. To total a long period, set a range that fits on one page or add the pages together.
To see the outside part purchases behind an OPP Amount, run OPP & Shop Paid Outs Report for the same dates.