You can assume 35 minutes in normal circumstances, timed from the scan at the FCC desk at the end of Fast Track. It can be less, below 25 minutes, but I've not worked out the full logic yet. I guess your mysterious destination may depart from B or C, in which case 35 minutes is a stretch, given that boarding could close at T-20 minutes (and will close at that time from A4). If you are one PNR then you could in theory be rebooked if your transfer time falls below 1 hour, but I can't believe they're tracking Lufthansa's flights.