A new watch which comes equipped with a deployant buckle (termed DB for short) usually requires a little setting up by its new owner. That is, if it has not already been done by the watch shop staff before leaving the shop.
Assuming it has not been done, setting up a watch leather band and deployant buckle is a fairly easy task.
The following is a step-by-step guide for setting this up. In this exercise, the Ball Trainmaster Worldtime Chronograph was used as an example as it features the butterfly-folding clasp commonly found on most other watch models.
How to Set Up a Deployant Buckle
That is all there is to it! If the watch feels tight or too loose around the wrist, redo Steps 2 to 7 above to readjust the pin hole on the watch strap. Ideally, the watch should wrap snugly around your wrist without choking it, or should not have too much freeplay moving around the wrist at every flip of your arm.