Modifying TNExpress Order Acknowledgement

We have an Order Acknowledgement that came with TNew.  I have been able to modify it for minor, cosmetic changes, but now I am trying to change something structural and have not yet been able to figure out what exactly needs changing.

The current acknowledgement lists a separate line for each seat in the order.  This is not a big deal for most orders from households, but when a school purchases 50 general admission seats, it makes us look silly to send out an email with all of those identical lines.

I am suspecting that it is the file CartHTML.xslt that controls how it is displayed, but beyond that I am out of my depth.  Has anyone else done this, and do you mind sharing how you suppress the repeated lines?

Thanks,

Clarke