add my currency on alchemy pay

hi everyone i am trying to add my currency on alchemy pay platform and i am facing a problem with the scenario
i made a price query api first as per this page https://alchemypay.readme.io/docs/price-query-1
user choose amount and fiat and click pay
-> fiat currency is paid from user credit card
-> alchemy pay notify me that the user paid (so i created a web hook to receive that as per this page https://alchemypay.readme.io/docs/webhook-notification)
-> i transfer the crypto amount to the user wallet (the logic for this is inside the notification api i just created)
-> says should be 1 more notification but can't understand also there is this page which i don't know should i implement it or not https://alchemypay.readme.io/docs/callback