Update of LIS in cancelled billing document

Dear Experts,

I have observed that in the cancelled billing document the update group is updated is 1. the original bill which was cancelled also have update group 1.

now i want to know how to correct it because this is wrong for surely, if both original and cancel bill has update group 1 then my billing data will come wrong in SIS.

also i have seen after cancelling the bill somebody has deleted the sales order ( because it was in showing open order), does this is causing the wrong update?