$100 * (5 / 31) = $16.13
and credits $16.13 to the subscription balance.For the new price, the remaining time until the next billing period is also 5 days.Nadles calculates the amount due for the remaining time as follows: $300 * (5 / 31) = 48.39
.The final payment amount due at the moment of upgrade is: $48.39 — $16.13 = $32.26
— this is the actual amount the customer will pay for the upgrade.On Feb 1, the customer will be charged the full amount of $300 for the next billing period.$300 * (5 / 31) = $48.39
and credits $48.39 to the subscription balance.For the new price, the remaining time until the next billing period is also 5 days.Nadles calculates the amount due for the remaining time as follows: $100 * (5 / 31) = 16.13
.The final payment amount due at the moment of upgrade is: $16.13 - $48.39 = -$32.26
.Since the credit balance is greater than the amount due, the amount due is simply deducted from the credit balance which now becomes $32.36.On Feb 1, the customer should be charged $100 for the next billing period of the new price.But since there is a remaining credit balance, it is applied to the payment and the actual charge will be $100 - $32.36 = $67.64
.