The value of points/banked rewards credited to a user by an admin can define in the Maximum Gifting Threshold field available in the role associated with the admin.
Platform-->Settings-->Admin Users-->Roles-->[Select any role]-->Maximum Gifting Threshold
For example, if the Maximum Gifting Threshold of a site admin role is 2. which means, all the admins with the site admin role can only credit maximum of 2 points to any guest.