A subscription product involves recurring billing based on the cycle you established when creating the product record. The next bill date is established based on this billing interval. Customers may occasionally ask you to change the next bill date so that the timing of the autocharge is more convenient. When you change the next bill date, the amount of the upcoming autocharge may also adjust if the "prorate" setting is enabled on the product's subscription plan. This setting is most often used for service products that involve access to a membership program or personal consulting / coaching because the service continues to be fulfilled, even though the bill date is changed.

The fulfillment of a physical product is not centered around time investment, so these types of products generally do not need to be prorated.

For Example: You run a marketing agency that charges clients a monthly fee of $1000 that includes up to 3 hours of work each month. You have a small business customer whose autocharge generally takes place at the beginning of the month. This customer contacts you and asks you to adjust the bill date so that the autocharges come after the 15th of the month. This change does not impact their access to your services - you continue to fulfill as normal, even though the date is changed.

If you move the next bill date forward (and the prorate setting is enabled), the system will automatically adjust the amount of the next autocharge. 

Pro-rating will not interrupt the current cycle if the date is moved further out, as the prorating calculations work on a per-cycle basis (i.e the start of each cycle), which is why one cannot move the next bill date past one cycle.
So in your example, if the next bill date is 10/25, the system will bill the normal amount when the date reaches 10/25, but then will prorate the next cycle (10/25 > 11/15).

After the next autocharge takes place, the amount billed will return to normal.

1. While viewing a contact record, click on the Order tab, and scroll to the Subscriptions section.
    
2. Click on the name of the subscription to modify it.
    
3. Go to the Current Status section and click on Change beside the next bill date.
   
   
    
4. Click the calendar icon to choose a new date for the next billing cycle.
   
   
    
5. Verify the new bill date is correct and click Save.

How to enable Autocharge on a subscription

1.  Go to Ecommerce>Products>search for your subscription that you want to enable prorating on. 
2.  Goto the Subscription Plans tab and click on the subscription that you wish to update. When the "Manage Subscription Plan" box pops up - check the Prorate box> Click Save