Being called an hour before a standby commences does NOT infringe the FTLs unless the call is made during the Rest Period. The rest period starts when the last duty ends. Except as described above, it is rare in my line of work to have the duty, rest period and next duty so tightly packed.
Let's say you were called an hour before your standby started to check in in an hour and a half.
As you tell us you know exactly how FTLs are calculated then perhaps you can tell us exactly how long your maximum FDP is and how you arrives at that figure.