[WebERP-developers] Z_DeleteInvoice don't clear invoiced_qty correctly

[Alessandro S. <ADS...@ac...>]

Hi all
Z_DeleteInvoice do not clear the qty_invoiced from the invoice to the sales order see line 121
	$SQL = "UPDATE salesorderdetails SET qtyinvoiced = qtyinvoiced - " . $OrderLine['qty'] . “,
as  $OrderLine[‘qty’] from stock moves is negative internally it’s adding it in reality so at the end of the deletion you end up with salesorderdetails.qtyinvoiced doubled instead of cleared.
Can i simply change the “-“ with “+” and all is well ? or there is a finer point that i don’t get ? 
thanks all 
Alessandro Saporetti