What happens if a new seat is added while an account is under a discount?

Additional seats added during a billing cycle with a discount will be charged at a prorated rate based on the discounted plan's pricing.

For instance, if I add 5 seats halfway through the monthly billing cycle, and I have a 50% discount applied to my plan, those 5 seats will be charged at 50% of the standard rate for the remaining days of the current billing cycle.