Add estimated Usage in Subscription

I am trying to add the Estimated usage in a Subscription following the document link mentioned below

https://docs.oracle.com/en/cloud/saas/subscription-management/fasum/bill-using-estimated-usage.html#Add-Estimated-Usage

Section in the URL - > Add Estimated Usage

We are unable to find the field where this Estimated Usage can be added.

Please let us know if there is any other setup required to add this Estimated Usage quantities or there is any gap in understanding

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