What does it change on a Friday night?
Not the cooking. A KDS does not make a grill hotter. What it removes is everything around the cooking: walking to a printer, hunting for a ticket, asking the front which app the tall bag belongs to, and remaking an order because the paper slid behind the line.
Run the arithmetic on your own numbers rather than trusting a brochure. If your kitchen does 120 tickets on a Friday and the screen saves 15 seconds of walking and squinting per ticket, that is 30 minutes of line labor back in one shift. If it prevents two remakes at a $12 food cost plus a refunded ticket, that is real money in a business that runs on single-digit margins.
The second change is measurement. Paper tickets give you a feeling about how the night went. A KDS gives you the actual time on every ticket, by station, by channel, by hour. That is the number to argue with when somebody says delivery orders are slowing down the dining room.