Let’s take out the COGS value in the Unspecified column, Karen.
Before we start, we’ll have an overview of this behavior first. In a normal process we, we buy the items, build an assembly and sell it. Then, your P&L by Class report will look perfect. However, if you un-build or delete an assembly and recreate it, after you record sales, it will result to your scenario. You'll incur a COGS amount under Unspecified. When you double-click that amount, you'll see that it's from your re-built assembly.
To resolve this, you'll need to deselect and re-select the assembly item on your sales transactions, then re-run the report after. You can try one transaction to see how it affects the COGS value on your report.
We're just around you need more help.