Accounting Issue for Serialized Depriciable Item

Hello,

I was applying test case to verify accounting effect of invoice price variance (IPV), during verification I got following accounting entries.

I observed that Inventory account is crediting twice, please suggest if I am missing any step.

Transaction	Account	Dr	Cr
PO Receipt	Receiving Account	100
	AP Accrual		100
PO Delivery	Inventory Account	100
	Receiving Account		100
Asset Addition	Asset Account	100
	Inventory Account		100
Invoice	AP Accrual	100
	Invoice Price Variance (IPV)	20
	Liability		120
Asset Adjustment	Asset Account	20
	Invoice Price Variance (IPV)		20
Issuance	Charge Account	100
	Inventory Account		100
Asset Retirement	Retirement (profit/loss account)	120
	Asset Account		120