I will explain the amount discount as it is eaisier. This is correct for discount before tax. If it was discount after tax, then the total discount would be 1. But for discount before tax:
Product price: 50
Product after discount: 49
Product total after discount including tax: 58.80
Product total no discount including tax: 60.
Total discount: 60-58.80=1.20
So discount you are seeing in the front end is the total discount, including any savings because of tax. Now if you look in AwoCoupon history, it should show that the amount discount was 1.