posting to stock transfer price variance account

I have stock transfer intracompany stock transfer transfer. Freight in the po is 10

posting is done as below at the time of goods issue

goods issuing plant bsx 100-

Goods receiving plant bsx 110

freight clearing account 1-

Stock transfer price variacne account 9-

As Per my understanding freight clearing account should have 10- value but it is only 1- difference is being posted to stock transfer price variance account.

I want the reason behind this.

I see in PO freight condition is of 10 , price for the material is standard. & movement type for goods issue is 351.

Thanks,

Kiran