One of the most likely reasons is that your school is in ‘By Theme’ mode. That’s to say, you’re set up to have orders on everyday be the same.
The report engine expects to find orders on the first day of each theme to be the same and so only shows one day, even though you may have changed the orders for some days later in the run.
As a temporary work around, you can force the report engine into showing all of the days by setting the check date – the date that ordering closes to be after the date of the first lunch orders. This triggers a switch and the report engine automatically shows all of the dates in the ordering run.