Hello,
The COGS should account should be the actual GL Account you want the Cost for selling the Item or Charge(Item) to post too. The Purchase Account and offsetting Direct Cost Applied Account are used during the first entry of Purchasing. For example:
Purchase Order of an Item:
1st Entry = Debit Purchase Account / Credit Accounts Payable
2nd Entry = Debit Inventory / Credit Direct Cost Applied
The Purchase and Direct Cost Applied account should wash to zero so they should be the same GL Account. Most users setup a Direct Cost Applied Account, in the COGS section of the Chart if Accounts, to post too.
Hope this helps.
Thanks,
Steve