How to calculate from burst and rate?

The getOrderAddress SP-API has a burst of 20 and a rate of 0.0055 requests per second. Am I correct it takes 1/0.0055 = 182 seconds to fill the bucket to 20? I need the country code for all orders on an invoice. This used to be in the Orders MWS-API, but now I need a separate call for each order?