Setting the Gallery Width of your products on the single product page is very easy with the WooGallery Pro plugin. Follow the steps below:

(1) Navigate to WooGallery Pro from your WordPress Dashboard Menu.

(2) Under the General settings tab, you will find the Gallery Width option. 

(3) Set the width value in percentage (%) as you want. 

(4) Finally, click on Save Settings and refresh the product gallery to see the changes.