As an administrator, when you assign keywords/credits to your users, they are automatically debited from your account counter even if they are not used.
It is a quota system and you have to be careful not to allocate too much.
RDV here for user management: https://account.myposeo.com/account/configuration/users#!?predicate=email&sort=a&r=50&page=1
Click on the edit icon in the Actions column at the end of the line of the selected user.
In the block named "Limit access to user", enter the number of credits and/or keywords you want to grant to the user. Click on the "Save User" button to validate your actions.