When an expense is recorded with a tax code, the automatic journal exports showing the amount of the expense less GST. So in my below example, the expense was a total of $10 with the tax code GST 10% on purchases. The expense line itself shows $9.09 and we see the 0.91 amount of GST recorded at the bottom of the page.
If you are seeing something different, it's possible the journal was edited after it was exported - you can check this by clicking the More option at the bottom of the journal, then Audit History. This lists all changes, timestamped by user and highlights where specific changes may have been made on the journal. Otherwise, I would recommend you contact our Support Team directly for this query so they can get eyes on the activity in your file and take steps from there as required: