If it's stock there is no firing order. Both cylinders spark on compression stroke at the same time. The one that's charged with fuel creates power while the other is considered a "wasted" spark because the cylinder isn't on a compression stroke at the time.
The first piston fires.
The next piston fires 315 degrees later.
There is a 405-degree gap.
The other piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
A little complex but it is easy to understand if you see an animation of it. There's one online, but it runs a little fast to really see the spark timing and not get confused......which I probably just made you even more
Very good explanation by BigAl. The reason for the 315/405 gap, is the 45 degree angle. Even though the pistons are moving on the same crank pin, the angle causes the difference of when the piston gets to the top. The attached link should help, you may need to click on the arrow below the engine to get it stripped.