TMFX v 1.93 MacOS (3)
RME Thunderbolt Settings Firmware: v112, Driver: v1.05
Fireface UFX+ (23919669) (the old hardware version, I guess: SW Version: 55, Active Nodes: 105)

The lowest 10 values of delay time (0 to 0.09 s) have negative OSC-values and thus cannot be set externally.
1. s == 0, so that is the lowest value you can set.
It may be related to the BPM value: the BPM value does not go higher than 800, if you set a value in TM FX smaller than 0.1 s.
For instance 0.09 and 0.08 both have a BPM value of 800.