Posting Date Difference in FI Document

Hi experts,

During GR and IR both posting date and document date are entered 31.01.2014. There were value and quantity variance in invoice receipt. So two FI documents are created automatically.

Transactional keys of FI documents are:

1st doc: Vendor, BSX, WRX, VST

2nd doc: BSX, UMB

Create date of invoive receipt is: 05.02.2013

Entered posting date and document date in invoice receipt are 31.01.2014

But, In 2nd FI document, posting date is 01.02.2014.

Please tell me the possible reasons.

Thanks,

Merve

PS. see the attached doc.