You will need to add some form of action based on which is chosen.
Ticket tag would be a simple solution and tags are reported in the default work period report.
You could add an automation command executed rule where the command name is the command name set in the ask question. This rule would want a update ticket tag action with say a ticket tag name of ‘Returning Customer’ and the tag value of [:CommandValue] (the yes or no) so you would get;
Returning Customer
Yes 90
No 100
These numbers would be ticket qty not customer qty, ie a ticket with orders for 4 customers entered as new would count as 1 No
I would think the best solution would be using the Ticket Logging feature and log the Command Value for button clicks to each ticket. You can then use reporting to get your totals.
We have {REPORT TICKET LOG DETAILS} and here is a good read on how to use this.