This is a bit of a twist. To use the parts selector module, you must also be using the store module. In order to manage the bubble numbers, you must look up the item in the store (Product Manager) and then click on the Parts tab. As you associate parts to the item, you will see there is a field for "bubble numbers" that you can easily update. Once the bubble number is saved, they will automatically display on your item as a parts.
Below is a video that you can use to understand how the bubble numbers are managed.