The minimum credit control quota values are one second for time quota and one byte for volume quota. These minimum values are not realistic deployment values for multiple reasons such as effective sampling periods, statistics processing time, RADIUS message load, subscriber scale, and so on.
For typical deployment scenarios it is not recommended to implement Credit Control quota values smaller than 60 seconds for time quota and for volume quota the volume that can be consumed in 60 seconds for that category (function of number of queues/policers monitored and their respective rates).