Multiple Payment entries showing same document number

we have some payment entries for which voucher number is different (E.G.1,2,3....) but Document Number is same for all the payment entries (E.G.1024249)

We checked our document number series in "Manage Payment Document" & we observed same bank has multiple account number & doc start number is assigned as below:

Can anyone help to understand how the same document number is assigned to different payment entry.

Bank Name	start no
SM AP HDFC Bank -123	1010001
ROM HDFC BANK-456	1000001
KERALA HDFC Bank -789	113709
SM KA HDFC Bank -001	1022173

                  

Bank   Name	start no
SM AP HDFC Bank -AAA	1010001
ROM HDFC BANK-BBB	1000001
KERALA HDFC Bank -CCC