How does the whole plan get changed when Tokyo went outside of the bank one second earlier?

.. what difference does it make if going outside of the bank one second earlier?

There was no difference, per se.. Rio's dialogue was apart of the acting.

Rio yelling for Tokyo to not go outside yet was the beginning of the "first act" of the robbery: convincing everyone (hostages included) that something had gone terribly wrong, and that they were trapped in the building.

Just before Tokyo and Rio go outside, it shows the Professor explaining this stage of the robbery:

"It's vital that the police don't have the slightest clue what we're up to .. We'll make them believe we came in for a robbery, they caught us by surprise leaving with the money and everything was f*ed up .. that we took out the guns and shot point-blank, and had no choice but to go back. .. And then, not hurting anybody, we get inside. Let them think we're trapped like rats. Let them think we're improvising."

Immediately after this, it cuts scene to Tokyo exclaiming that the time is now for them to go outside, with Rio proceeding to start the acting by yelling at Tokyo that it's too early to go out there.

Not only was this dialogue from Rio pertinent for getting the robbers in the proper mindset to play their roles, but it also served to convince the hostages of this illusion.

Anyhow, Tokyo was supposed to shoot blanks at the police and come back inside.

Tokyo was supposed to shoot live rounds, but only at the ground, and at a point-blank distance.

TOKYO: "Go out, throw the money, shoot at the ground and go back. I'd heard that more than 30 times."