Follow this guide if you want your customers to be able to book several participants on a specific service - for example Personal Training for two customers at once.
First you will need to create a capacity type:
Go to Configuration > Staff and resources > Capacity types
Create a new one by clicking on the plus sign +
This is just a label that later will be used to connect the capacity to the resource and the service product
After creating the capacity type you need to add it to the resource. This is also where you set the maximum capacity:
Go to Configuration > Staff and resources > Resources
Click on the resource that will be added to the service product
Scroll down and click on the plus sign + under "Capacity"
Choose the capacity type you created earlier and add the maximum capacity (the amount of customers who should be able to book the service at the same time)
Now you need to add the same capacity type to the service product:
Go to Configuration > Products > Products
Go to the service product
Go to the "Resource requirements" tab > click on your added resource
Under "Capacity", add your capacity type and check the "May split resource" box.