Many businesses take bookings rather than make immediate sales. For example, restaurants, nail bars, dentists and so on.
If you run this type of business, a conversion is getting a booking and if you want to take bookings online, which you should if you are after immediate conversions via your QR Code campaign, you can use some powerful online booking applications. Some of these integrate directly into third party calendar systems.
You can also search for apps by following this link.