According to this URL: Reference | Twitch Developers
The response contains ‘id’ that says “An ID that identifies the entitlement.”
I decoded it by base64 encoding. And I found a format: “{user_id}|{benefit_id}|{strange_string}”
I guess strange_string also mean unique identifier of the entitlement.
Please confirm my guess is right.
Id’s are to be treated as opaque strings. What they can or can’t be encoded as should not matter as that can change at any time and without warning, much like it has with other opaque strings that are not intended to be worked with beyond the fact that they’re a string and in this case are globally unique.