The 25 services per day cap is a rolling 24-hour window applied to newer accounts, separate from the Pro plan's 100 services per project limit. As your earlier service creations age out of the 24-hour window, you'll be able to create more. Creating different projects won't help since this limit is account-level, not project-level.

Can you increase this limit as I am testing something out? Just this once?

The 25 services per day cap is a fixed safeguard for newer accounts and cannot be raised, even temporarily. As your earlier service creations fall outside the rolling 24-hour window, you'll be able to create more.

If somebody were to test out service creation in their app, and the number is > 25, how would they go about it?

The 25 services per day cap is account-level and applies to newer accounts on a rolling 24-hour window. If your app needs to programmatically create more than 25 services in a day, you would need to spread the creation across multiple days or wait for your account to mature past the newer-account threshold, as this limit cannot be raised or bypassed.

what is the newer account threshold exactly? how long do I have to wait to not remain as a "new account"?

The exact threshold for when an account is no longer considered "new" is not published, and it is determined by internal criteria that we don't disclose. In the meantime, the rolling 24-hour window means you can continue creating services in batches of 25 per day.