GDI: draft invoice items amount is not equal to cust rev dist lines amount for a credit invoice.

I have a draft invoice for amount (say) 1000. This draft is a partial credit of invoice. But in pa_cust_rev_dist_lines_all table for this draft invoice(credit) sum of lines is more than 1000. I could fine 5 lines which are not in sync with draft invoice and cust rev dist lines.

Anyone seen this before? Is some setup causing it?