The credits on your account depending on the plan you purchased. Credit refers to the number of minutes your plans include.
1 credit is equivalent to 1 minute. 180 credits remaining refers to 3 hours unused credits on your account.
Eg. Your account has 300 credits and you requested a task that took 25 minutes to complete. You will then have 275 credits left on your account.
Go to your Dashboard to have the summary of the total used credits and/or the remaining credits left for the billing cycle. Go To My Menu >>Dashboard