If you are looking at JC_M  Work in Process Summary report, the NET WIP (last column) represents the $ value  difference between the value at which the completed units went into finished goods (i.e. std cost) and the work order total actual costs.  This remaining value represents the company's investment of the uncompleted units, work in process.  This number is not posted to the GL nor does it appear on the financial statements.  
 
Only when a work order is closed, does the WIP variance post to the general ledger (i.e. financial statements) .  It represents the difference between the work order actual incurred costs and the costs that were transferred to finished production for all units on the work order. Specfically to which account it posts, depends on what account is set up in the default WIP variance (this default is set up in the Accounting module, AD-A, General Ledger Defaults, and click on the bottom left button that reads Manufacturing GL accounts)
 
Hope this helps.