You will not be charged for additional credits while your workflow is "on-hold".

Duration timer : will continue to run while a job is "on hold".

Credits: Will not be charged for workflows that are in a hold state waiting for manual approval. The hold state doesn't require any resources, therefore no additional credits are consumed while jobs are "on-hold".

More information on credit charges can be found on our pricing page -- in addition, we have some further details in our documentation.

Jobs and steps that ran before the approval step those jobs would have consumed credits to run.