Cookie yields can be difficult to estimate. For consistent baking, cookies should be generally uniform in size, but there is no need to become preoccupied with the size or shaping. Do the best you can. Use the recipe yields, along with the directions for shaping and dropping cookies, as guides. If there is a little range in the final products, the lucky taster who gets the biggest cookie will be happy. The unlucky taster who gets the smallest can seize the excuse to go in for seconds.
A showcase of cookie videos for inspiration and helpful technique demonstrations is available at vimeo.com/showcase/10471279.