Failsafe is supposed to trigger immediately; if you have hangtime it will try to level at 0 power for that interval; failsafe disarm is supposed to take the configured interval.
That is, if you have a hangtime timer set to 3s, and a failsafe disarm timer set for 10s:
at 0.25s: it will go into failsafe + hangtime; it will be willing to spin motors to try and stabilize, at as close to 0 power as it can run. If the TX reconnects during this time, you have full control and all these timers restart.
at 3.25s: motors will spin at idle (if spin when idle is checked) with no stablization. any servos used (e.g. fixed wing) will still be trying to seek the appropriate failsafe stabilization (e.g. for fixed wing, a slow right banking turn). If the TX reconnects during this time, you have full control and all these timers restart.
at 10.25s: motors will -stop-.. Spinning motors again will require going through your arming sequence.