You can create a promo code for a single ticket and the code will work for that specific ticket only. Just you have to make sure that the Ticket Price should be greater than the promo code discount (if you enter Code Type as Amount).
You can add a single promo code for all paid tickets or else you can create separate promo codes for each of them.
ℹ️ Users can use this promo code for all the paid tickets till the usage limit exceeds and it's enabled and is within the valid duration.
🔺To know about creating a common promo code for all tickets go to Common Promo Code