How are Affiliate Commissions handled for subscription upgrades?

We are using Membership plugin with affiliate plugin.

Inside each subscription plan, there is an option called "Affiliate payment credited for a signup on this subscription" that allows us to enter the commission when a user subscribes.

We want to know what "AMOUNT" gets credited or debited to the affiliate when a user upgrades or downgrades from one subscription plan to another?

Example:
Subscription A = Free and $0 in Affiliate payment credited for a signup

Subscription B = $20/month and $20 in Affiliate payment credited for a signup

Subscription C = $50/month and $50 in Affiliate payment credited for a signup

Using example above:

How much gets paid to affiliate if a user upgrades from Subscription A to Subscription B ?

How much gets paid to affiliate if a user upgrades from Subscription B to Subscription C ?

What happens to affiliate commission If user downgrades from Subscription C to Subscription B?

Thanks!