It was definitely few seconds for Shanks to leave his ship and beat Kid. But I'm talking about how long it would take for:
1) Kid to charge up his attack
2) Kid to release the attack
3) Attack to take the effect
Because what Shanks saw was the
end point of the attack.
Look at the page:
Basically, we have enough time for:
1) Kid to start preparing the attack and Shanks to notice that
2) Shanks to give orders to his crew (several seconds)
3) Shanks and Ben to comment on the damage
4) Shanks to fly over to Kid and for Kid to notice him and comment on it
In my estimate, just the dialogue between Shanks noticing and him launching himself at Kid would take some 15 seconds
at least. More like 20 - 25 seconds if they are not speedtalking. Add another couple of seconds for Shanks to reach Kid and beat him, and several more seconds that Kid will have taken to launch his attack and attack to reach the fleet had Shanks not stopped him, and it may have taken comfortably more than half a minute.
So shorter than my original estimate, but definitely more than a few seconds into the future.
On the flip side, I just noticed that Kid himself said "I'll annihilate all of you in 10 seconds", meaning that all of the above goes out of the water as we actually have a solid timeframe for how long Kid's attack will have taken to take effect. So not only is Shanks a good speed-talker but he is ridiculously fast as well. Chances are, he reached Kid in maybe one second after the end of the dialogue?
Not using her haki...
because she is distressed.