One of the most common formatting questions we get asked at Cinovation is, "should I number my Scene Headings in a film script?"
The only time Scene Headings are numbered is when a script is in production and they need to track the scenes being shot. When you're writing a script for submission, do not number scenes in a film script.
Now, if you want to number your scenes for some personal reason while you're writing, that's fine. But don't submit a film script with scene numbers.
In a Sitcom or Television script, scenes are always numbered (or lettered) with the Scene Number element. But, again, the Scene Headings in the Sitcom or TV script are not numbered (they never are).
By the way, with Scriptware, when you're ready to number scenes, it just takes one mouse click (or a couple keystrokes). Then, if you want to track revisions with A&B pages and scenes, Scriptware does that automatically!