Normally, when you have posted GR, the amount 6451.10 is credited in GR/IR balance account.
When you cancelled the GR then the amount 6451.10 should debited into GR/IR balance account.
But here, I suppose after GR from any transaction someone must debit the GR/IR amount for 2956.34, that's because when you have done cancellation, the rest amount 3494.76 is debited to GR/IR account.
Have you checked MB5S for GR/IR balance.