It seems useful to briefly explain how I label my drafts.

It is of note that I don't share draft numbers with outside folks; when I submit a work for consideration, I simply submit it without any reference to which draft number I'm on. This is because early draft numbers come across as unready, and large numbers come across as unproven. That said, I am sharing my process here, and so explaining my taxonomy seems relevant.

Draft numbering, for me, is not a one-to-one with the actual number of iterations I've written, but rather a statement of readiness to be consumed.

I tend to start with my first full draft being around 0.5 or 0.6; this is simply the first time I have a complete story done, with the ones preceding those being partial states. From there I work through in 0.n increments until I have something that I feel is ready for its first table read. This one is what I call my first draft; Draft 1.0.

The loose taxonomy of drafts for me is:

Draft n.0 - Ready to be read.
Draft n.1 - Mostly unaltered version of Draft 1.0 with only typos fixed and with all notes from the read/performance embedded in the script.
Draft n.2 thru n.9 - All the real work between drafts.

Actually, to be completely honest, Draft n.0 means both that it's ready for consumption, and that I've gone blind; that I can no longer objectively evaluate the quality of the work, and I have to hear trained professionals read it out loud.

Given this, the general life of one of my scripts will be: draft 0.5 when I have a story done and I solicit feedback (collaborators, respected peers, my dramaturg, and - of course - my wife), draft 1.0 when it receives its first table read, draft 2.0 its second, and it is not until draft 3.0 when it will finally have reached the starting point for a staged reading or a production.

But, this is just me. For my fellow writers who may read this, I'd love to hear your approach.