Discount not properly enforced when purchase quantity exceeds discounted stock l

Hello,
I’m experiencing an issue with the Sales Countdown Timer Premium plugin where the discount is being applied incorrectly when customers purchase quantities that exceed the discounted stock limit.
Setup Example:

Product A: 100 units total stock
Regular price: €100
Discounted price: €80 (20% off)
Discounted quantity limit: First 20 units only

Problems:

Discount applied beyond limit: When a customer purchases more than 20 units (even all 100 units), the discount is applied to the entire order instead of only the first 20 units. For example, if someone buys 30 units, all 30 receive the €80 price instead of only the first 20.
Discount incorrectly split across orders: If one customer buys 19 units and another buys 81 units, the second customer receives the discount on all 81 units instead of just 1 unit (the remaining discounted stock).
Cancelled orders not restored: When an order is cancelled, the discounted stock count is not restored. For example, if 10 discounted units are purchased (leaving 10 remaining) and then the order is cancelled, the plugin doesn’t restore the count back to 20 available discounted units.

The discount should only apply to the specified quantity limit and should properly track and restore stock when orders are cancelled.
Thank you for your assistance.