Subscription Quantity Not Working

[PercivalLive]

Hi, I have generated this subscription link: https://www.paypal.com/webapps/billing/plans/subscribe?plan_id=P-0H35520213095605CMXTKB4Q
The subscription plan if of type "Quantity pricing" but if you click the link above, you can see that the quantity is set to 1 and grayed out:

I need my clients to be able to set the number of items they want or at least I have to be able to set a different number when generating the link.

I don't want to use the API or create a button with code. I just want to generate a link I can share and people can click on it to subscribe.

Thanks!