How many credits actually have to be raised for a crawl can only be guessed in advance. If all settings in the crawl setup are done, an estimation of the required page credits is provided in the right field.
How many page credits do I have left? When do they fill up again?
You can find an overview of your available resources under Settings > Licenses > Overview.
There you can also see the start date of the license period. That indicates when the credits will be recharged. For example, the license started on 03/05/2019. This means that the credits refill every month on the 05th.