They are inaccurate.
They are logged into chat as a user and are reading the IRC USERNOTICE events.
These bots can also read chat and see whom has a “subscriber” badge and guestimate there.
Which only accounts for new subs, and resubs that choose to share their sub. And they have to guess when people unsub or don’t renew. And have no record of the ultra lurkers.
Poll the API, you only need to get the partner to login/grant you access once (or when they change/reset their password or the token expires/cannot be renewed). Was that not clear from the documentation you don’t want me to link to?
Personally depending on $otherStuff I either perform a fetch daily and then update with incoming pubsub data on the subscribers feed. Or Fetch every 3 hours for other applications. Most of the partners I work with authenticated months ago, and I only need a new token when the current one expires for whatever reason.
TLDR:
- You are working with a partner,
- get them to authorise (once) with the relevant scopes,
- poll the API periodically.
Personally, poll no quicker than once per three hours for a full fetch, and once per 5 minutes if you are just after the total.