User is trying to create an invoice from expense entries, but the markups on the expense entries increase significantly after creating the invoice.
This can happen if you edit the Billable Expense amount and set it to a higher value in the Invoice Batch screen when creating the invoice. This adjusts the Net Bill and total expense amount on the invoice, and also marks up all the linked expense entries, so that their total Charge Amount matches the amount billed on the invoice. Check CORE Help Center for details.