The Scene Number indicates that you're starting a new scene. Scene numbers are usually only used in Sitcom or Play scripts (in film scripts that are in production, the Scene Heading will be numbered, but that's a different story -- see Numbering?).
Scene Numbers look like this:SCENE II SCENE THREE SCENE 7 SCENE P
The numbering style you use depends on both your taste and/or the style in use by the show for which you're writing. In other words, if you're writing a "Cybill" script, use the numbering style that they use (more about this in Give 'em what they want.)
Sometimes you will repeat the Act Number above the Scene Number like:ACT V SCENE 2
Then, the next scene is:ACT V SCENE 3
Some shows start renumbering the Scenes for each act, others let the Scene Numbers just continue to add sequentially. For example, this:ACT SIX ACT SIX ACT SEVEN SCENE D SCENE E SCENE F
versus:ACT SIX ACT SIX ACT SEVEN SCENE D SCENE E SCENE A
Like you would with Act Numbers, sometimes you will indicate the end of the Scene by putting END OF SCENE X at the end of the previous scene.
Scene Numbers are uppercase and centered horizontally. If the Scene Number follows the Act Number, put one blank line before the Scene Number. Otherwise, put the Scene Number 2" from the top of the page. Start each new scene on a new page.
If a show uses letters instead of numbers for each scene it typically will not use certain letters. Most commonly, shows will not use the letters "i" or "o" because the capital versions of those letters look too much like the numbers one and zero.
If you have more than 26 scenes, start numbering from the 27th like this: AA BB CC DD EE FF, etc.
If you use an End Of Scene indicator, put 2 blank lines between it and the last line of the previous scene.
When both an Act and a Scene end, just use the End Of Act indicator.
To start a new scene, with the cursor on a blank line, just type "scene" and press <Enter>.
Scriptware will start a new page, put the scene in the proper margins with the proper spacing, uppercase and centered with the correct number (or letter) and, if you want, it will put the Act Number above the Scene Number and an End Of Scene indicator on the previous page... automatically!