PayPal is offering $5 off a $10 purchase at Subway to the first 50,000 customers using this promo before May 30, 2019.
All you have to do is click on “Use Offer” to save the deal to your PayPal Wallet. Then shop through the Subway app and pay for your order with PayPal at checkout. Your $5 discount will then be automatically applied to your purchase. Please note, your discount will not be displayed when checking out in app, but will be applied automatically to your qualifying purchase as long as you have successfully loaded the offer to your PayPal account. You can verify this by checking your PayPal “Wallet” section after you've clicked “Save Offer.”
The promo didn't start until today, so I'd imagine this will be available for at least another few days. I don't see it lasting until May 30 though.