Leoben is in Upper Styria, in the Upper Mur Valley. The SwiftStop there is a parking stop. It isn’t listed as an overnight spot for motorhomes. If you’re looking for a camper night, that’s a different SwiftStop.
You can park there during the day or for a month. Both apply from the time of purchase for the stated period. This does not mean a camper night.
Here, too, you don’t reserve in advance. The other SwiftStops are meant for passing through with a motorhome: arrive, scan the QR code, pay, no account. Don’t apply that to Leoben as long as there’s no overnight product for campers listed there.